Vehicle control device

ABSTRACT

An FB distribution rule  20  determines an actual vehicle actuator operation control input and a vehicle model operation control input such that a difference between a reference state amount determined by a vehicle model  16  and an actual state amount of an actual vehicle  1  (a state amount error) approximates to zero, and the control inputs are used to operate an actuator device  3  of the actual vehicle  1  and the vehicle model  16.  In the FB distribution law  20,  when an actual vehicle feedback required amount based on the state amount error exists in a dead zone, then an actual vehicle actuator operation control input is determined by using the required amount as a predetermined value. A vehicle model manipulated variable control input is determined such that a state amount error is brought close to zero, independently of whether an actual vehicle feedback required amount exists in a dead zone. This enhances linearity of a control system and also enhances the robustness against disturbance factors or changes therein while carrying out operation control of an actuator that suits a behavior of an actual vehicle as much as possible.

TECHNICAL FIELD

The present invention relates to a control device for a vehicle having aplurality of wheels, such as an automobile (engine automobile), a hybridcar, and a two-wheeled motor vehicle.

BACKGROUND ART

A vehicle, such as an automobile, is provided with systems, including adriving/braking system that transmits a driving force from a propulsiveforce generating source, such as an engine, to wheels or imparts abraking force, a steering system (steering control system) forcontrolling the steering control wheels of a vehicle, and a suspensionsystem that elastically supports a vehicle body on wheels, as mainmechanisms. Furthermore, in recent years, there has been known a vehicleprovided with a variety of electric or hydraulic actuators to actively(positively) control the operations of the actuators according to atraveling condition of the vehicle or an environmental condition or thelike rather than merely passively operating the systems in response tooperations (man-caused operations) of a steering wheel (driver's wheel),an accelerator (gas) pedal, a brake pedal and the like performed by adriver, as shown in, for example, Japanese Patent Laid-Open No.2000-41386 (hereinafter referred to as patent document 1).

Patent document 1 proposes a technology for determining the feedforwardtarget value of a rear wheel steering angle on the basis of a frontwheel steering angle, and for determining the feedback target value ofthe rear wheel steering angle on the basis of a difference between areference state amount (a reference yaw rate and a reference lateralacceleration) and an actual state amount (a yaw rate detection value anda lateral acceleration detection value), and then making the rear wheelsteering angle follow the sum of the target values. In this case, thereference state amount is set on the basis of a front wheel steeringangle. Further, the parameters or gains of transfer functions of afeedforward controller, a feedback controller, and a reference stateamount determiner are adjusted on the basis of an estimated value of afriction coefficient of a road surface.

However, the technology disclosed in the above-mentioned patent document1 has been presenting the following inconveniences. The behaviors of anactual vehicle are subjected to the influences of a variety ofdisturbance factors, including changes in a friction coefficient of aroad surface.

Meanwhile, it is practically difficult to sequentially generate optimumreference state amounts while taking all disturbance factors intoaccount by using a vehicle model or the like. For instance, according tothe one in patent document 1, although the parameters or the like of thetransfer functions of the reference state amount determiner are adjustedon the basis of an estimated value of the friction coefficient of a roadsurface, actual vehicle behaviors are influenced by a variety offactors, such as variations in the characteristics of wheel tires,variations in the characteristics of the devices of a steering systemand the like, estimation errors of friction coefficients, and modelingerrors of a model for generating reference state amounts, in addition tothe friction coefficient of a road surface.

Thus, according to the technology disclosed in patent document 1, thereare cases where a variety of disturbance factors causes a referencestate amount to be relatively significantly remote from a motion stateof an actual vehicle. In such a case, an operation of a vehicle actuatoris controlled on the basis of a control input that is unsuited to anactual vehicle behavior or the operation of the actuator is restrictedby a limiter, thus making it difficult to ideally control the operationof the actuator.

Further, frequent use of a braking system of a vehicle by automaticcontrol may cause the braking system (especially a brake pad, a brakedisc or the like) to become hot. Hence, a brake manipulated variable inthe automatic control is usually provided with a dead zone. As a result,however, a control system of the vehicle has been exhibiting a nonlinearcharacteristic, which inconveniently leads to deteriorated robustness ofthe vehicle control, as compared with the case where no dead zone isprovided.

The present invention has been made in view of the background describedabove, and it is an object thereof to provide a vehicle control devicecapable of enhancing the linearity of a control system and enhancingrobustness against disturbance factors or changes therein while carryingout control of the operations of actuators that suits behaviors of anactual vehicle as much as possible.

DISCLOSURE OF INVENTION

To fulfill such an object, according to the present invention of avehicle control device,

there is provided a vehicle control device equipped with a drivemanipulated variable detecting means which detects a drive manipulatedvariable that indicates a drive manipulation state of the vehicle drivenby a driver of the vehicle having a plurality of wheels, an actuatordevice provided in the vehicle so as to permit the manipulation of apredetermined motion of the vehicle, and an actuator device controlmeans which sequentially controls an operation of the actuator device,the vehicle control device, comprising:

an actual state amount grasping means for detecting or estimating afirst actual state amount, which is a value of a predetermined firststate amount related to a predetermined motion of an actual vehicle;

a model state amount determining means for determining a first modelstate amount, which is a value of the first state amount related to apredetermined motion of the vehicle on a vehicle model establishedbeforehand as a model expressing dynamic characteristics of the vehicle,on the basis of at least the detected drive manipulated variable;

a state amount error calculating means for calculating a first stateamount error, which is a difference between the detected or estimatedfirst actual state amount and the determined first model state amount;and

an actual vehicle state amount error response control means and a modelstate amount error response control means, which respectively determinean actual vehicle actuator operation control input for operating theactuator device of the actual vehicle and a vehicle model operationcontrol input for manipulating the predetermined motion of the vehicleon the vehicle model on the basis of at least the calculated first stateamount error such that the first state amount error is approximated tozero,

wherein the actuator device control means is a means which controls theoperation of the actuator device on the basis of at least the determinedactual vehicle actuator operation control input,

the model state amount determining means is a means which determines thefirst model state amount on the basis of at least the detected drivemanipulated variable and the determined vehicle model operation controlinput,

the actual vehicle state amount error response control means comprises ameans which determines an actual vehicle feedback required amount by afeedback control law on the basis of the first state amount error and ameans which determines the actual vehicle actuator operation controlinput on the basis of at least the actual vehicle feedback requiredamount, and the means which determines the actual vehicle actuatoroperation control input is a means which determines the actual vehicleactuator operation control input by using a predetermined value setbeforehand in a predetermined dead zone in place of the actual vehiclefeedback required amount when the actual vehicle feedback requiredamount lies in the dead zone, and

the model state amount error response control means is a means whichdetermines the vehicle model operation control input such that at leastthe first state amount error is approximated to zero regardless ofwhether the actual vehicle feedback required amount lies in the deadzone or not (a first invention).

According to the first invention, basically, the operation of anactuator device of the actual vehicle is feedback-controlled by theactual vehicle actuator operation control input so as to approximate thefirst state amount error to zero, and a vehicle motion on the vehiclemodel and eventually the first model state amount are manipulated by themodel operation control input so as to approximate the first stateamount error to zero. This arrangement prevents an actual vehicle motionand a vehicle motion on the vehicle model from becoming considerablyapart from each other due to influences of disturbance factors or thelike.

And, at this time, if the actual vehicle feedback required amount, thatis, a required amount for approximating the first state amount error tozero, lies in a predetermined dead zone, then the actual vehicle stateamount error response control means determines an actual vehicleactuator operation control input by using a predetermined value in thedead zone instead of an actual vehicle feedback required amount (inother words, by regarding that an actual vehicle feedback requiredamount is held at the predetermined value). Therefore, even if an actualvehicle feedback required amount fluctuates in the dead zone, thefluctuation is not reflected on an actual vehicle actuator operationcontrol input, thus restraining the operation of an actuator device fromfrequently changing on the basis of a first state amount error. If anactual vehicle feedback required amount deviates from a dead zone, thenan actual vehicle actuator operation control input may be determined onthe basis of the actual vehicle feedback required amount or the amountof the deviation of the actual vehicle feedback required amount from thedead zone. The dead zone is desirably a range in the vicinity of a value(e.g., zero) of an actual vehicle feedback required amount in the casewhere a first state amount error is steadily held at zero. Further, apredetermined value in the dead zone desirably agrees with a value of anactual vehicle feedback required amount in the case where a first stateamount error is steadily held at zero.

Meanwhile, in the case where an actual vehicle feedback required amountis in a dead zone, the actual vehicle actuator operation control inputdetermined when the first state amount error is not zero does not havethe function for bringing the first state amount error close to zero.However, according to the first invention, the model state amount errorresponse control means determines the vehicle model operation controlinput such that at least the first state amount error is approximated tozero independently of whether an actual vehicle feedback required amountexists in a dead zone. For example, a feedback required amountdetermined by the feedback control law from the first state amount erroris directly used as it is (without carrying out dead zone processing) todetermine the vehicle model operation control input. Thus, the firststate amount related to a motion of the vehicle on the vehicle model isbrought close to the first state amount related to a motion of theactual vehicle. This allows the first state amount error to approximatezero without hindrance, making it possible to avoid alienation of amotion of the vehicle on the vehicle model and a motion of the actualvehicle.

Hence, it is possible to restrain the operation of an actuator device ofan actual vehicle from frequently changing according to a first stateamount error, thus preventing a motion of the vehicle on the vehiclemodel from being alienated from a motion of the actual vehicle. As aresult, according to the first invention, the robustness againstdisturbance factors or changes therein can be enhanced while carryingout the control of the operations of actuators that suits behaviors ofthe actual vehicle as much as possible.

The first state amount does not have to be one type of state amount, andit may be a plurality of types of state amounts. An actual vehicleactuator operation control input may be, for example, a target value (atarget manipulated variable) that defines an operation of the actuatordevice. Further, an actual vehicle feedback required amount includes,for example, an external force (a moment or a translational force, orboth thereof) to be additionally applied to the actual vehicle. Further,a vehicle model operation control input includes, for example, a virtualexternal force (a moment or a translational force, or both thereof) tobe additionally applied to the vehicle on the vehicle model.

In the first invention, preferably, the first state amount includes astate amount related to a rotational motion of the vehicle in yawdirection, the actuator devices include an actuator device capable ofmanipulating at least the difference between right and leftdriving/braking forces, which is the difference between thedriving/braking forces of a pair of right and left wheels of the actualvehicle, and the actual vehicle actuator operation control inputincludes at least one of the target driving/braking forces of the pairof right and left wheels and a target slip ratio, the manipulatedvariable of the actuator device associated with the targetdriving/braking forces or the target slip ratio, and the manipulatedvariable of the difference between the right and left driving/brakingforces (a second invention).

According to the second invention, the operation of an actuator deviceof the actual vehicle is basically controlled by the actual vehicleactuator operation control input such that the first state amount errorrelated to a rotational motion in the yaw direction of the vehicle (forexample, the difference between the yaw rate of the actual vehicle andthe yaw rate of the vehicle on the vehicle model) is approximated tozero. In this case, the actuator device capable of manipulating thedifference between the right and left driving/braking forces, which isthe difference between the driving/braking forces of the right and leftwheels of the actual vehicle is included among the actuator devices, sothat at least one of the target driving/braking forces of the wheels, atarget slip ratio, the manipulated variable of the actuator deviceassociated with the target driving/braking forces or the target slipratio, and the manipulated variable of the difference between the rightand left driving/braking forces is included in the actual vehicleactuator operation control input thereby to manipulate the differencebetween the right and left driving/braking forces, thus making itpossible to apply an external force (moment) for approximating a firststate amount error to zero to the actual vehicle. Furthermore, in thiscase, when the actual vehicle feedback required amount lies in a deadzone, the occurrence of a situation wherein the difference between theright and left wheel driving/braking forces frequently varies can bereduced.

Further, preferably, the first or the second invention described aboveis provided with a means for determining the amount of deviation of arestriction object amount, the value of which is defined by at least oneof a second state amount related to a motion of the actual vehicle and asecond state amount related to a motion of the vehicle on the vehiclemodel, from a predetermined permissible range, and the model stateamount error response control means determines the vehicle modeloperation control input such that the first state amount error and thedetermined amount of deviation approximate to zero independently ofwhether the actual vehicle feedback required amount exists in the deadzone or not (a third invention).

According to the third invention, the vehicle model operation controlinput is determined such that the amount of deviation of a predeterminedrestriction object amount from a predetermined permissible range and thefirst state amount error are approximated to zero. This makes itpossible to determine a first model state amount such that a motion ofthe vehicle on the vehicle model will be a motion easily followed by amotion of the actual vehicle (a motion in which a restriction objectamount falls within a permissible range). As a result, the robustness ofthe control of a vehicle can be further enhanced.

Alternatively, preferably, the first or the second invention describedabove is provided with a means for determining the amount of deviationof a restriction object amount, the value of which is defined by atleast one of a second state amount related to a motion of the actualvehicle and a second state amount related to a motion of the vehicle onthe vehicle model, from a predetermined permissible range, wherein themeans for determining the actual vehicle feedback required amount is ameans which determines the actual vehicle feedback required amount by afeedback control law such that the first state amount error and thedetermined amount of deviation are approximated to zero (a fourthinvention).

According to the fourth invention, the actual vehicle actuator operationcontrol input is determined such that the amount of deviation of apredetermined restriction object amount from a predetermined permissiblerange and the first state amount error are approximated to zero. Hence,at least in a situation wherein the actual vehicle feedback requiredamount deviates from the dead zone, an actual vehicle actuator operationcontrol input can be determined such that the deviation of therestriction object amount from the permissible range is restrained. As aresult, the robustness of the control of a vehicle can be furtherenhanced.

Alternatively, preferably, the first or the second invention describedabove is equipped with a means for determining the amount of deviationof a restriction object amount, the value of which is defined by atleast one of a second state amount related to a motion of the actualvehicle and a second state amount related to a motion of the vehicle onthe vehicle model, from (a predetermined permissible range, and a meansfor determining a feedback auxiliary required amount by a feedbackcontrol law such that the amount of deviation is approximated to zero,wherein the means for determining the actual vehicle feedback requiredamount is a means for determining the actual vehicle feedback requiredamount by the feedback control law such that the first state amounterror is approximated to zero, and the means for determining the actualvehicle actuator operation control input is a means which determines theactual vehicle actuator operation control input on the basis of a valueobtained by correcting the predetermined value on the basis of at leastthe feedback auxiliary required amount when the actual vehicle feedbackrequired amount lies in the dead zone, and determines the actual vehicleactuator operation control input on the basis of a value obtained bycorrecting the actual vehicle feedback required amount on the basis ofat least the feedback auxiliary required amount when the actual vehiclefeedback required amount does not lie in the dead zone (a fifthinvention).

According to the fifth invention, the actual vehicle actuator operationcontrol input is determined such that the amount of the deviation of apredetermined restriction object amount from a predetermined permissiblerange is approximated to zero regardless of whether the feedbackrequired amount for approximating the actual vehicle feedback requiredamount, i.e., the first state amount error, to zero lies in a dead zone.Moreover, if an actual vehicle feedback required amount does not existin a dead zone, then the actual vehicle actuator operation control inputis determined such that the first state amount error is approximated tozero in addition to approximating the amount of the deviation to zero.This makes it possible to determine an actual vehicle actuator operationcontrol input such that the deviation of the restriction object amountfrom the permissible range is always restrained and also that an actualvehicle actuator operation control input will not excessively frequentlychange according to a first state amount error. As a result, therobustness of the control of a vehicle can be further enhanced.

The second state amount described above may be the same type of stateamount as the first state amount described above; however, it does nothave to necessarily be the same type of state amount as the first stateamount. The second state amount is preferably a state amount associatedwith the first state amount through the intermediary of a differentialequation. A restriction object amount and the second state amount may bea plurality of types of state amounts. Further, the third invention andthe fourth invention or the fifth invention may be combined.

In each of the third invention to the fifth invention described above,in the case where the first state amount includes a state amount relatedto a rotational motion in the yaw direction of the vehicle, therestriction object amount preferably includes at least one of a latestvalue of a state amount related to a lateral translational motion of theactual vehicle or the vehicle on the vehicle model or a value obtainedby filtering the state amount or a future predicted value of the stateamount, and a latest value of a state amount related to a rotationalmotion in the yaw direction of the actual vehicle or the vehicle on thevehicle model or a value obtained by filtering the state amount or afuture predicted value of the state amount (a sixth invention, a seventhinvention, and an eighth invention).

According to the sixth invention to the eighth invention, basically, theoperation of an actuator device of an actual vehicle is controlled bythe aforesaid actual vehicle actuator operation control input such thatthe first state amount error related to a rotational motion in the yawdirection of the vehicle (e.g., a difference between a yaw rate of anactual vehicle and a yaw rate of the vehicle on the vehicle model) isapproximated to zero. Therefore, the operation control eventuallymanipulates a component of a road surface reaction force acting from aroad surface onto each wheel of the actual vehicle, the component beingparallel to the road surface or the horizontal plane. In this case, atleast one of a latest value of a state amount related to a lateraltranslational motion of an actual vehicle or the vehicle on the vehiclemodel or a value obtained by filtering the state amount or a futurepredicted value of the state amount, and a latest value of a stateamount related to a rotational motion in the yaw direction of an actualvehicle or the vehicle on the vehicle model or a value obtained byfiltering the state amount or a future predicted value of the stateamount is included in the restriction object amount, thereby making itpossible to determine the first model state amount while preventing acomponent of a road surface reaction force which is parallel to a roadsurface or a horizontal component thereof, the road surface reactionforce acting from a road surface onto each wheel of an actual vehicle orthe vehicle on the vehicle model, or a centrifugal force acting on thevehicle (a centripetal force acting on the vehicle attributable to theresultant force of the road surface reaction forces acting on thewheels) from becoming excessive. As a result, the first model stateamount can be determined to permit proper control of the operation of anactuator device for approximating a motion of the actual vehicle to amotion of the vehicle on the vehicle model (to make it difficult for arestriction object amount related to a motion of the actual vehicle todeviate from a permissible range).

The first state amount may include a state amount related to a lateraltranslational motion of a vehicle in addition to a state amount relatedto a rotational motion in the yaw direction of the vehicle.

In each of the sixth invention to the eighth invention described above,preferably, the restriction object amount includes a latest value of ayaw rate of the actual vehicle or the vehicle on the vehicle model or avalue obtained by filtering the yaw rate or a future predicted value ofthe yaw rate, and the permissible range for the yaw rate is apermissible range set on the basis of at least an actual travelingvelocity such that the permissible range narrows as the actual travelingvelocity, which is a value of a traveling velocity of the actualvehicle, increases (a ninth invention, a tenth invention, and aneleventh invention).

In other words, when it is assumed that the yaw rate remains constant, acentrifugal force generated in a vehicle increases as the travelingvelocity of the vehicle increases. Hence, according to the ninthinvention to the eleventh invention described above, the first modelstate amount can be determined such that a centrifugal force generatedin the actual vehicle or the vehicle on the vehicle model does notbecome excessive.

According to the ninth invention to the eleventh invention, thetraveling velocity of the vehicle on the vehicle model will agree withthe traveling velocity of the actual vehicle. Further, the permissiblerange in the ninth invention to the eleventh invention may be set on thebasis of the characteristic of friction between the wheels of the actualvehicle and a road surface (e.g., an estimated value of a frictioncoefficient) in addition to an actual traveling velocity.

In the sixth invention or the ninth invention described above,preferably, the restriction object amount includes a latest value of astate amount related to a lateral translational motion of the actualvehicle or the vehicle on the vehicle model or a value obtained byfiltering the state amount or a future predicted value of the stateamount, and the vehicle model operation control input includes at leasta control input component which generates a moment in the yaw directionabout the center-of-gravity point of the vehicle on the vehicle model (atwelfth invention).

According to the twelfth invention, the vehicle model operation controlinput includes at least a control input component which generates amoment in the yaw direction about the center-of-gravity point of thevehicle on the vehicle model, so that it is possible to properlyprevent, by the vehicle model operation control input, the restrictionobject amount which includes a latest value of a state amount related toa lateral translational motion of an actual vehicle or the vehicle onthe vehicle model or a value obtained by filtering the state amount or afuture predicted value of the state amount from deviating from apermissible range. A technology equivalent to the twelfth invention maybe adopted in the seventh invention, the eighth invention, the tenthinvention, and the eleventh invention described above.

BEST MODE FOR CARRYING OUT THE INVENTION

The following will explain embodiments of the vehicle control device inaccordance with the present invention.

First, referring to FIG. 1, a schematic construction of a vehicle in theembodiments in the present description will be explained. FIG. 1 is ablock diagram showing the schematic construction of the vehicle. Avehicle illustrated in the embodiments in the present description is acar provided with four wheels (two wheels each at the front and the rearof the vehicle). The construction itself of the car may be a publiclyknown one, so that detailed illustration and explanation will be omittedin the present description.

As shown in FIG. 1, a vehicle 1 (car) is provided with a driving/brakingdevice 3A (a driving/braking system) that imparts a rotational drivingforce (a rotational force that provides an impelling force for thevehicle 1) to driving wheels among four wheels W1, W2, W3, and W4, orimparts a braking force (a rotational force that provides a brakingforce for the vehicle 1) to each of the wheels W1 to W4, a steeringdevice 3B (a steering system) for controlling steering control wheelsamong the four wheels W1 to S4, and a suspension device 3C (a suspensionsystem) that resiliently supports a vehicle body 1B on the four wheelsW1 to W4, as with a publicly known regular car. The wheels W1, W2, W3,and W4 are a front left wheel, a front right wheel, a rear left wheel,and a rear right wheel, respectively, of the vehicle 1. Further, thedriving wheel and the steering control wheel are the two front wheels W1and W2 in the embodiments to be explained in the present description.Hence, the rear wheels W3 and W4 are driven wheels andnon-steering-control wheels.

However, the driving wheels may alternatively be the two rear wheels W3and W4 or both the front wheels W1, W2 and the rear wheels W3, W4 (thefour wheels W1 through W4). Further, the steering control wheels mayinclude not only the two front wheels W1 and W2 but the rear wheels W3and W4 also.

These devices 3A, 3B and 3C have functions for manipulating the motionsof the vehicle 1. For example, the driving/braking device 3A has afunction for mainly manipulating the motions in advancing directions ofthe vehicle 1 (positions, velocities, accelerations and the like in theadvancing directions of the vehicle 1). The steering device 3B has afunction for mainly manipulating the rotational motions in the yawdirection of the vehicle 1 (postures, angular velocities, angularaccelerations and the like in the yaw direction of the vehicle 1). Thesuspension device 3C has a function for primarily manipulating themotions in the pitch direction and the roll direction of a vehicle body1B of the vehicle 1 (postures and the like in the pitch direction andthe roll direction of the vehicle body 1B of the vehicle 1) or themotions in the vertical directions of the vehicle body 1B (mainly aheight of the vehicle body 1B from a road surface (a vertical positionof the vehicle body 1B relative to the wheels W1 to W4)). Incidentally,a “posture” of the vehicle 1 or the vehicle body 1B means a spatialorientation in the present description.

Supplementally, in general, side slips of the wheels W1 to W4 occur whenthe vehicle 1 makes turns or the like. The side slips are subjected tothe influences of the steering angles of the steering control wheels ofthe vehicle 1, a yaw rate (an angular velocity in the yaw direction) ofthe vehicle 1, the driving/braking forces of the wheels W1 to W4, andthe like. For this reason, the driving/braking device 3A and thesteering device 3B have functions for manipulating the translationalmotions in lateral directions (right/left directions) of the vehicle 1.Incidentally, the “driving/braking force” of a wheel means atranslational force component, which is in a longitudinal direction ofthe wheel, of a road surface reaction force acting on the wheel from aroad surface (more specifically, in the direction of a line ofintersection between a rotational plane of the wheel (a plane whichpasses the central point of the wheel and which is orthogonal to therotational axis of the wheel) and a road surface or a horizontal plane).Further, in the road surface reaction force, a translational forcecomponent in the direction of the width of a wheel (the directionparallel to the rotational axis of the wheel) is referred to as a“lateral force.” In the road surface reaction force, a translationalforce component in a direction perpendicular to a road surface or ahorizontal plane is referred to as a “ground contact load.”

Although not detailedly illustrated, more specifically, thedriving/braking device 3A is equipped with a driving system constructedof an engine (an internal-combustion engine) serving as a motive powergenerating source of the vehicle 1 (an impellent force generating sourceof the vehicle 1) and a motive power transmitting system fortransmitting an output (a rotational driving force) of the engine to thedriving wheels among the wheels W1 to W4, and a braking device (abraking system) that imparts braking forces to the wheels W1 to W4. Themotive power transmitting system includes a transmission, a differentialgear, and the like.

The vehicle 1 explained in the embodiments is equipped with an engine asa motive power generating source; however, it may alternatively be avehicle provided with an engine and an electric motor as motive powergenerating sources (a so-called parallel type hybrid vehicle) or avehicle provided with an electric motor as a motive power generatingsource (a so-called electric car or a series type hybrid vehicle).

Further, a steering wheel (driver's wheel), an accelerator (gas) pedal,a brake pedal, a shift lever, and the like functioning as manipulatingdevices 5 (man-induced manipulating devices) operated by a driver tosteer the vehicle 1 (car) are provided in a vehicle interior of thevehicle 1. The illustration of the elements of the manipulating devices5 is omitted.

The steering wheel among the manipulating devices 5 is related to anoperation of the steering device 3B. More specifically, as the steeringwheel is rotationally manipulated, the steering device 3B is operated inresponse thereto, thus steering the steering control wheels W1 and W2among the wheels W1 to W4.

The accelerator (gas) pedal, the brake pedal, and the shift lever amongthe manipulating devices 5 are related to the operations of thedriving/braking device 3A. More specifically, the opening of a throttlevalve provided in the engine changes according to a manipulated variable(a depression amount) of the accelerator (gas) pedal so as to adjust anintake air volume and a fuel injection amount of the engine(consequently an output of the engine). Further, the braking device isoperated according to a manipulated variable (a depression amount) of abrake pedal, and a braking torque based on the manipulated variable ofthe brake pedal is imparted to the wheels W1 to W4. Further,manipulating the shift lever changes an operation state of thetransmission, such as a change gear ratio of the transmission, thuseffecting the adjustment or the like of the driving torque transmittedfrom the engine to the driving wheels.

The drive manipulation states of the manipulating devices 5, such as thesteering wheel operated by the driver (the steerer of the vehicle 1) aredetected by appropriate sensors, which are not shown. Hereinafter,detection values (detection outputs of the sensors) of the drivemanipulation states will be referred to as drive operation inputs. Thedrive operation inputs include the detection values of a steering angle,which is a rotational angle of the steering wheel, an accelerator (gas)pedal manipulated variable, which is a manipulated variable of theaccelerator (gas) pedal, a brake pedal manipulated variable, which is amanipulated variable of the brake pedal, and a shift lever position,which is a manipulation position of the shift lever. The sensors thatoutput the drive operation inputs correspond to the drive manipulatedvariable detecting means in the present invention.

In the embodiments in the present description, the driving/brakingdevice 3A and the steering device 3B described above are adapted topermit active control of the operations thereof (consequently themotions of the vehicle 1) in response to not only the drive operationinputs but also factors other than the drive operation inputs (e.g., amotion state of the vehicle 1 or an environmental condition), where “topermit active control” means that the operations of the devices 3A and3B can be controlled into the operations obtained by correcting basicoperations based on the drive operation inputs (basic desired operationsdetermined on the basis of drive operation inputs).

More specifically, the driving/braking device 3A is a driving/brakingdevice having a function that makes it possible to actively control thedifference or the ratio between a driving/braking force of the leftwheels W1, W3 and a driving/braking force of the right wheels W2, W4 onat least one of the pair of the front wheels W1, W2 and the pair of therear wheels W3, W4 through the intermediary of actuators, such as ahydraulic actuator, an electric motor, and an electromagnetic controlvalve, provided in the driving/braking device 3A (hereinafter, thecontrol function will be referred to as the right/left motive powerdistribution control function).

To be more specific, according to the embodiments in the presentdescription, the driving/braking device 3A is a driving/braking devicecapable of actively controlling the driving/braking forces to be appliedto the wheels W1 to W4 (specifically, the driving/braking forces in thebraking direction of the vehicle 1) by operating a braking devicethrough the intermediary of actuators provided in the braking device (adriving/braking device capable of controlling the driving/braking forcesto be applied to the wheels W1 to W4 by the braking device by increasingor decreasing the basic driving/braking forces determined on the basisof the manipulated variables of the brake pedal). Hence, thedriving/braking device 3A is a driving/braking device capable ofactively controlling, through the intermediary of the actuators, thedifference or the ratio between a driving/braking force of the leftwheels W1, W3 and a driving/braking force of the right wheels W2, W4 bythe braking device on both pairs, namely, the pair of the front wheelsW1, W2 and the pair of the rear wheels W3, W4 (a driving/braking devicethat has the right/left motive power distribution control function forboth pairs of the pair of the front wheels W1, W2 and the pair of therear wheels W3, W4).

The driving/braking device 3A may have a function that permits activecontrol, through the intermediary of actuators provided in the drivingsystem, of the difference or the ratio between the driving/brakingforces to be applied to the front wheels W1 and W2, which are drivingwheels, by operating the driving system of the driving/braking device3A, in addition to the function for actively controlling thedriving/braking forces of the wheels W1 to W4 by operating the brakingdevice.

As the driving/braking device 3A having the right/left motive powerdistribution control function as described above, a publicly known onemay be used.

Supplementally, the driving/braking device 3A having the right/leftmotive power distribution control function as described above will havea function for actively manipulating a rotational motion in the yawdirection of the vehicle 1 or a translational motion in the lateraldirection by the control function thereof.

Incidentally, the driving/braking device 3A includes an actuator forgenerating braking torque for the braking device, an actuator fordriving a throttle valve of the engine, an actuator for driving a fuelinjection valve, an actuator for performing speed change drive of thetransmission, and the like in addition to the actuators associated withthe right/left motive power distribution control function.

Further, the steering device 3B is a steering device capable ofsecondarily steering the front wheels W1 and W2 by an actuator, such asan electric motor, as necessary, in addition to, for example, a functionfor mechanically steering the front wheels W1 and W2, which are steeringcontrol wheels, through the intermediary of a steering mechanism, suchas a rack-and-pinion, according to a rotational operation of thesteering wheel (a steering device capable of controlling the steeringangle of the front wheels W1 and W2 by increasing or decreasing thesteering angle mechanically determined on the basis of the rotationalangle of the steering wheel).

Alternatively, the steering device 3B is a steering device which steersthe front wheels W1 and W2 by using only a driving force of an actuator(a so-called steering-by-wire steering device) Therefore, the steeringdevice 3B is a steering device capable of actively controlling thesteering angle of the front wheels W1 and W2 through the intermediary ofan actuator (hereinafter referred to as an active steering device).

If the steering device 3B is an active steering device which secondarilysteers the steering control wheels by an actuator in addition tomechanically steering the steering control wheels according to arotational operation of the steering wheel (hereinafter, such an activesteering device will be referred to as an actuator-assisted steeringdevice), then the resultant angle of the steering angle of a steeringcontrol wheel mechanically determined by a rotational operation of thesteering wheel and a steering angle based on an operation of an actuator(a correction amount of a steering angle) will be the steering angle ofthe steering control wheel.

If the steering device 3B is an active steering device which steers thesteering control wheels W1 and W2 by using only a driving force of anactuator (hereinafter, such an active steering device will be referredto as an actuator-driven type steering device), then a target value ofthe steering angle of the steering control wheels is determined on thebasis of at least a detection value of the steering angle and theactuator is controlled such that the actual steering angle of thesteering control wheels takes the target value.

As the steering device 3B capable of actively controlling the steeringangle of the steering control wheels W1 and W2 through the intermediaryof an actuator (the active steering device), a publicly known one may beused.

The steering device 3B in the embodiments in the present description isan active steering device capable of actively controlling the steeringangle of the front wheels W1 and W2 through the intermediary of anactuator; alternatively, however, it may be a type that performs onlythe mechanical steering of the front wheels W1 and W2 on the basis of arotational operation of the steering wheel (hereinafter referred to as amechanical type steering device). Further, in a vehicle having allwheels W1 to W4 as steering control wheels, the steering device may becapable of actively controlling the steering angles of both the frontwheels W1, W2 and the rear wheels W3, W4 through the intermediary ofactuators. Alternatively, the steering device may be a type which steersthe front wheels W1 and W2 on the basis of a rotational operation of thesteering wheel only by a mechanical means, such as a rack-and-pinion,and which is capable of actively controlling only the steering angle ofthe rear wheels W3 and W4 through the intermediary of an actuator.

According to the embodiments in the present description, the suspensiondevice 3C is a suspension device which passively operates on the basisof, for example, a motion of the vehicle 1.

However, the suspension device 3C may be a suspension device capable ofvariably controlling, for example, a damping force, hardness or the likeof a damper interposed between the vehicle body 1B and the wheels W1 toW4 through the intermediary of an actuator, such as an electromagneticcontrol valve or an electric motor. Alternatively, the suspension device3C may be a suspension device capable of directly controlling a stroke(an amount of vertical displacement between the vehicle body 1B and thewheels W1 to W4) of a suspension (a mechanical portion, such as aspring, of the suspension device 3C) or a vertical expanding/contractingforce of the suspension generated between the vehicle body 1B and thewheels W1 to W4 by a hydraulic cylinder or a pneumatic cylinder (aso-called electronically controlled suspension). If the suspensiondevice 3C is a suspension device capable of controlling the dampingforce or the hardness of the damper and the stroke or theexpanding/contracting force of the suspension as described above(hereinafter referred to as the active suspension device), then thesuspension device 3C permits active control of the operations thereof.

In the following explanation, among the driving/braking device 3A, thesteering device 3B, and the suspension device 3C, those devices capableof actively controlling the operations as described above may bereferred to generically as actuator devices 3. In the embodiments in thepresent description, the actuator devices 3 include the driving/brakingdevice 3A and the steering device 3B. If the suspension device 3C is anactive suspension device, then the suspension device 3C is also includedin the actuator devices 3.

Further, the vehicle 1 is provided with a controller 10 which determinesa manipulated variable of an actuator (a control input to the actuator;hereinafter referred to as an actuator manipulated variable) provided ineach of the actuator devices 3 on the basis of the above-mentioned driveoperation inputs and the like, and controls the operation of each of theactuator devices 3 on the basis of the actuator manipulated variable.This controller 10 is constituted of an electronic circuit unit thatincludes a microcomputer and the like, and it receives the driveoperation inputs from sensors of the manipulating devices 5 and also thedetection values of the state amounts of the vehicle 1, such as atraveling velocity, a yaw rate and the like of the vehicle 1, andinformation on traveling environments and the like of the vehicle 1 fromvarious sensors, which are not shown. Then, based on those inputs, thecontroller 10 sequentially determines actuator manipulated variables ata predetermined control processing cycle so as to sequentially controlthe operations of the actuator devices 3.

The above has described the general schematic construction of thevehicle 1 (the car) of the embodiments in the present description. Thisschematic construction will be the same in all embodiments to beexplained below.

Supplementally, according to the embodiments in the present description,among the driving/braking device 3A, the steering device 3B, and thesuspension device 3C described above, those corresponding to theactuator devices in the present invention (the actuator devices to whichthe present invention will be applied to carry out operation control)will be the driving/braking device 3A or the driving/braking device 3Aand the steering device 3B. Further, the controller 10 corresponds tothe actuator device controlling means in the present invention.

Further, the controller 10 implements a variety of means in the presentinvention by the control processing function thereof.

First Embodiment

The control processing by a controller 10 in a first embodiment will nowbe schematically explained by referring to FIG. 2. FIG. 2 is afunctional block diagram showing an overview of an entire controlprocessing function of the controller 10. In the following explanation,a real vehicle 1 will be referred to as an actual vehicle 1.

The portion excluding the actual vehicle 1 in FIG. 2 (more precisely,the portion excluding the actual vehicle 1 and sensors included in asensor/estimator 12, which will be discussed later) corresponds to theprimary control processing function of the controller 10. The actualvehicle 1 in FIG. 2 is provided with the driving/braking device 3A, thesteering device 3B, and the suspension device 3C described above.

As illustrated, the controller 10 is equipped with, as its mainprocessing function components, the sensor/estimator 12, a referencemanipulated variable determiner 14, a reference dynamic characteristicsmodel 16, a subtracter 18, a feedback distribution law (FB distributionlaw) 20, a feedforward law (FF law) 22, an actuator operation targetvalue synthesizer 24, and an actuator drive control unit 26. Thesolid-line arrows in FIG. 2 indicate primary inputs to the processingfunction components and the dashed-line arrows indicate secondary inputsto the processing function components.

The controller 10 carries out the processing by these processingfunction components at a predetermined control processing cycle tosequentially determine actuator manipulated variables at each controlprocessing cycle. Further, the controller 10 sequentially controls theoperations of the actuator devices 3 of the actual vehicle 1 on thebasis of the actuator manipulated variables.

The following will present an outline of each processing functioncomponent of the controller 10 and an outline of the overall processing.Hereinafter, regarding the values of the variables determined at eachcontrol processing cycle of the controller 10, a value finally obtainedby the processing at a current (a latest) control processing cycle willbe referred to as a current time value, and a value finally obtained bya last time control processing cycle will be referred to as a last timevalue.

At each control processing cycle, the controller 10 first detects orestimates a state amount of the actual vehicle 1 or a state amount of atraveling environment of the actual vehicle 1 by the sensor/estimator12. In the present embodiment, detection targets or estimation targetsof the sensor/estimator 12 include, for example, a yaw rate γact, whichis an angular velocity in the yaw direction of the actual vehicle 1, atraveling velocity Vact (ground speed) of the actual vehicle 1, avehicle center-of-gravity point side slip angle βact, which is a sideslip angle of the center-of-gravity point of the actual vehicle 1, afront wheel side slip angle βf_act, which is a side slip angle of thefront wheels W1 and W2 of the actual vehicle 1, a rear wheel side slipangle βr_act, which is a side slip angle of the rear wheels W3 and W4 ofthe actual vehicle 1, a road surface reaction force (a driving/brakingforce, a lateral force, and a ground contact load), which is a reactionforce acting on the wheels W1 to W4 of the actual vehicle 1 from a roadsurface, a slip ratio of the wheels W1 to W4 of the actual vehicle 1,and a steering angle δf_act of the front wheels W1 and W2 of the actualvehicle 1.

Among these detection targets or estimation targets, the vehiclecenter-of-gravity point side slip angle βact is an angle formed by thevector of the traveling velocity Vact of the actual vehicle 1 withrespect to the longitudinal direction of the actual vehicle 1 when theactual vehicle 1 is observed from above (on the horizontal plane). Thefront wheel side slip angle βf_act is an angle formed by the advancingvelocity vector of the front wheels W1 and W2 with respect to thelongitudinal direction of the front wheels W1 and W2 when the actualvehicle 1 is observed from above (on the horizontal plane). The rearwheel side slip angle βr_act is an angle formed by the advancingvelocity vector of the rear wheels W3 and W4 with respect to thelongitudinal direction of the rear wheels W3 and W4 when the actualvehicle 1 is observed from above (on the horizontal plane) The steeringangle δf_act is an angle formed by the rotational surfaces of the frontwheels W1 and W2 with respect to the longitudinal direction of theactual vehicle 1 when the actual vehicle 1 is observed from above (onthe horizontal plane).

The front wheel side slip angle βf_act may be detected or estimated oneach of the front wheels W1 and W2; alternatively, however, thedetection or the estimation may be performed by representativelydefining the side slip angle of one of the front wheels W1 and W2 asβf_act, or the detection or the estimation may be performed by defininga mean value of the side slip angles of both as βf_act. The same appliesto the rear wheel side slip angle βr_act.

Further, the estimation targets of the sensor/estimator 12 include acoefficient of friction between the wheels W1 to W4 of the actualvehicle 1 and an actual road surface in contact therewith (hereinafter,an estimated value of the friction coefficient will be referred to asthe estimated friction coefficient μestm). Preferably, the processingfor estimating a friction coefficient includes filtering of low-passcharacteristics so as to restrain frequent fluctuation in the estimatedfriction coefficient μestm. In the present embodiment, the estimatedfriction coefficient μestm is an estimated value of, for example, arepresentative value or a mean value of the coefficient of the frictionbetween the wheels W1 to W4 and a road surface. Alternatively, however,the estimated friction coefficient μestm may be determined for each ofthe wheels W1 to W4 or the estimated values of the estimated frictioncoefficient μestm may be determined separately on the pair of the frontwheels W1, W2 and the pair of the rear wheels W3, W4, or separately onthe pair of the front wheel W1 and the rear wheel W3 on the left sideand the pair of the front wheel W2 and the rear wheel W4 on the rightside.

The sensor/estimator 12 is equipped with various sensors mounted on theactual vehicle 1 to detect or estimate the above-mentioned detectiontargets or estimation targets. The sensors include, for example, a ratesensor for detecting angular velocities of the actual vehicle 1, anacceleration sensor for detecting accelerations in the longitudinaldirection and the lateral direction of the actual vehicle 1, a velocitysensor for detecting the traveling velocity (ground speed) of the actualvehicle 1, a rotational velocity sensor for detecting the rotationalvelocities of the wheels W1 to W4 of the actual vehicle 1, and a forcesensor for detecting road surface reaction forces acting on the wheelsW1 to W4 of the actual vehicle 1 from a road surface.

In this case, for an estimation target that cannot be directly detectedby a sensor installed in the actual vehicle 1 among the detectiontargets or the estimation targets, the sensor/estimator 12 estimates theestimation target by an observer or the like on the basis of a detectionvalue of a state amount related to the estimation target or the value ofan actuator manipulated variable determined by the controller 10 or atarget value defining it. For instance, the vehicle center-of-gravitypoint side slip angle βact is estimated on the basis of mainly adetection value of the acceleration sensor installed in the actualvehicle 1. Further, for example, the friction coefficient is estimatedby a publicly known method on the basis of mainly a detection value ofthe acceleration sensor.

Supplementally, the sensor/estimator 12 has a function as an actualstate amount grasping means in the present invention. In the presentembodiment, the type of a first state amount related to vehicle motionsuses a vehicle yaw rate and a vehicle center-of-gravity point side slipangle. In this case, the yaw rate has a meaning as a state amountrelated to the rotational motions in the yaw direction of the vehicle,and the vehicle center-of-gravity point side slip angle has a meaning asa state amount related to the lateral translational motions of thevehicle. Further, the yaw rate γact and the vehicle center-of-gravitypoint side slip angle βact are detected or estimated by thesensor/estimator 12 as a first actual state amount in the presentinvention.

Hereinafter, the designations of the state amounts or the like of theactual vehicle 1 to be detected or estimated by the sensor/estimator 12will be frequently accompanied by “actual.” For instance, the yaw rateγact of the actual vehicle 1, the traveling velocity Vact of the actualvehicle 1, and the vehicle center-of-gravity point side slip angle βactof the actual vehicle 1 will be referred to as the actual yaw rate γact,the actual traveling velocity Vact, and the actual vehiclecenter-of-gravity point side slip angle βact, respectively.

Subsequently, the controller 10 determines, by a reference manipulatedvariable determiner 14, a reference model manipulated variable as aninput to a reference dynamic characteristics model 16, which will bediscussed later. In this case, the reference manipulated variabledeterminer 14 receives a drive operation input detected by a sensor ofthe manipulating devices 5 and determines the reference modelmanipulated variable on the basis of at least the drive operation input.

More specifically, in the present embodiment, the reference modelmanipulated variable determined by the reference manipulated variabledeterminer 14 is the steering angle of the front wheels of a vehicle ona reference dynamic characteristics model 16, which will be discussedlater, (hereinafter referred to as the model front wheel steeringangle). To determine the model front wheel steering angle, a steeringangle θh (current time value) of the drive operation input is input as amain input amount to the reference manipulated variable determiner 14.The actual traveling velocity Vact (current time value) and theestimated friction coefficient μestm (current time value) detected orestimated by the sensor/estimator 12, and a state amount (last timevalue) of the vehicle on the reference dynamic characteristics model 16are also input to the reference manipulated variable determiner 14.Further, the reference manipulated variable determiner 14 determines themodel front wheel steering angle on the basis of these inputs.Basically, the model front wheel steering angle may be determined on thebasis of the steering angle θh. In the present embodiment, however, apredetermined restriction is placed on the model front wheel steeringangles input to the reference dynamic characteristics model 16. To placethe restriction, Vact, μestm and the like in addition to the steeringangle θh are supplied to the reference manipulated variable determiner14.

Supplementally, the type of reference model manipulated variablegenerally depends on the form of the reference dynamic characteristicsmodel 16 or the type of state amount to be determined by the referencedynamic characteristics model 16. The reference dynamic characteristicsmodel 16 may include the reference manipulated variable determiner 14.If the reference dynamic characteristics model 16 is constructed torequire a drive operation input itself, then the reference manipulatedvariable determiner 14 may be omitted.

Subsequently, the controller 10 determines and outputs a reference stateamount, which_is the state amount of a reference motion of the actualvehicle 1 (hereinafter referred to as the reference motion), by thereference dynamic characteristics model 16. The reference dynamiccharacteristics model 16 is a model which is established beforehand andwhich represents dynamic characteristics of a vehicle, and itsequentially determines a state amount of a reference motion (areference state amount) on the basis of predetermined inputs, includingthe reference model manipulated variable mentioned above. The referencemotion basically means an ideal motion or a motion close thereto of theactual vehicle 1 which is considered desirable to a driver.

In this case, the reference dynamic characteristics model 16 receivesmainly the reference model manipulated variable determined by thereference manipulated variable determiner 14 and control inputs(feedback control inputs) Mvir and Fvir for operating the referencedynamic characteristics model 16 determined by an FB distribution law20, which will be discussed later, and determines a reference motion(eventually the time series of a reference state amount) on the basis ofthe inputs.

More specifically, in the present embodiment, a reference state amountdetermined and output by the reference dynamic characteristics model 16is composed of a set of a reference state amount related to a rotationalmotion in the yaw direction of a vehicle and a reference state amountrelated to a translational motion in the lateral direction of a vehicle.A reference state amount related to the rotational motion in the yawdirection of the vehicle is, for example, a yaw rate reference value γd(hereinafter referred to as the reference yaw rate γd in some cases) andthe reference state amount related to the translational motion in thelateral direction of the vehicle is, for example, a vehiclecenter-of-gravity point side slip angle reference value βd (hereinafterreferred to as the reference vehicle center-of-gravity point side slipangle βd in some cases). To sequentially determine these reference stateamounts γd and βd at each control processing cycle, the model frontwheel steering angle (current time value) and the feedback controlinputs Mvir and Fvir (last time values) as reference model manipulatedvariables are supplied. In this case, according to the presentembodiment, the traveling velocity of the vehicle on the referencedynamic characteristics model 16 is set to agree with the actualtraveling velocity Vact. Thus, the actual traveling velocity Vact(current time value) detected or estimated by the sensor/estimator 12 isalso supplied to the reference dynamic characteristics model 16. Then,based on these inputs, the reference dynamic characteristics model 16determines the yaw rate and the vehicle center-of-gravity point sideslip angle of the vehicle on the reference dynamic characteristics model16 and outputs the determined results as the reference state amounts γdand βd.

Incidentally, the feedback control inputs Mvir and Fvir supplied to thereference dynamic characteristics model 16 are feedback control inputsadditionally supplied to the reference dynamic characteristics model 16in order to restrain alienation (separation) between a motion of theactual vehicle 1 and a reference motion (or approximating a referencemotion to a motion of the actual vehicle 1) due to, for example, achange in a traveling environment (such as a road surface condition) ofthe actual vehicle 1 (a change not considered in the reference dynamiccharacteristics model 16), a modeling error in the reference dynamiccharacteristics model 16, or a detection error or an estimation error ofthe sensor/estimator 12. In the present embodiment, the feedback controlinputs Mvir and Fvir are virtual external forces virtually applied tothe vehicle on the reference dynamic characteristics model 16. Mvir ofthe virtual external forces Mvir and Fvir denotes a virtual moment inthe yaw direction which is to act about the center-of-gravity point ofthe vehicle 1 on the reference dynamic characteristics model 16, andFvir denotes a virtual translational force in the lateral directionwhich is to act on the center-of-gravity point.

Supplementally, the reference state amounts γd and βd correspond to thefirst model state amount in the present invention, and the referencedynamic characteristics model 16 corresponds to a vehicle model in thepresent invention. Further, the processing by the reference manipulatedvariable determiner 14 and the reference dynamic characteristics model16 constitutes the model state amount determining means in the presentinvention.

Subsequently, the controller 10 calculates, by a subtracter 18, a stateamount error, which is the difference between the actual state amount(the same type of an actual state amount as a reference state amount)detected or estimated by the sensor/estimator 12 and the reference stateamount determined by the reference dynamic characteristics model 16.

More specifically, the subtracter 18 determines, as state amount errors,the differences γerr(=γact−γd) and βerr(=βact−γd) between the values(current time values) of the actual yaw rate γact and the actual vehiclecenter-of-gravity point side slip angle βact and the values (currenttime values) of the reference yaw rate γd and the reference vehiclecenter-of-gravity point side slip angle βd determined by the referencedynamic characteristics model 16.

Supplementally, the processing by the subtracter 18 constitutes thestate amount error calculating means in the present invention. Further,the state amount errors γerr and βerr determined by the subtracter 18correspond to the first state amount errors in the present invention.

Subsequently, the controller 10 supplies the state amount errors γerrand βerr determined as described above to the FB distribution law 20.The FB distribution law 20 determines the virtual external forces Mvirand Fvir, which are feedback control inputs for manipulating thereference dynamic characteristics model 16 and an actuator operationfeedback target value (actuator operation FB target value), which is afeedback control input for manipulating the actuator devices 3 of theactual vehicle 1.

In the present embodiment, the actuator operation FB target valueincludes a feedback control input related to the operation of thebraking device of the driving/braking device 3A (more specifically, afeedback control input for manipulating a driving/braking force to beapplied to the wheels W1 to W4 by operating the braking device).Alternatively, the actuator operation FB target value includes afeedback control input related to the operation of the steering device3B (more specifically, a feedback control input for manipulating thelateral forces of the front wheels W1 and W2 by operating the steeringdevice 3B) in addition to a feedback control input related to theoperation of the driving/braking device 3A. The actuator operation FBtarget value is, in other words, a feedback control input formanipulating (correcting) a road surface reaction force, which is anexternal force to be applied to the actual vehicle 1.

The FB distribution law 20 basically determines the virtual externalforces Mvir and Fvir and the actuator operation FB target value suchthat the received state amount errors γerr and βerr are approximated tozero. However, when determining the virtual external forces Mvir andFvir, the FB distribution law 20 determines the virtual external forcesMvir and Fvir such that not only the state amount errors γerr and βerrare approximated to zero but the deviation of a predeterminedrestriction object amount of the actual vehicle 1 or the vehicle on thereference dynamic characteristics model 16 from a predeterminedpermissible range is restrained. Further, the FB distribution law 20determines, as the actuator operation FB target value, a feedbackcontrol input related to the operation of the braking device of thedriving/braking device 3A or a feedback control input related to theabove feedback control input and the operation of the steering device 3Bsuch that a predetermined moment in the yaw direction for approximatingthe state amount errors γerr and βerr to zero is generated about thecenter-of-gravity point of the actual vehicle 1 (more generally, suchthat a predetermined external force (road surface reaction force) forapproximating the state amount errors γerr and βerr to zero acts on theactual vehicle 1).

To determine the virtual external forces Mvir, Fvir and the actuatoroperation FB target value, the FB distribution law 20 receives not onlythe state amount errors γerr and βerr but also at least one of thereference state amounts γd and βd, which are outputs of the referencedynamic characteristics model 16, and the actual state amounts γact andβact detected or estimated by the sensor/estimator 12. Furthermore, theFB distribution law 20 also receives actual state amounts, such as theactual traveling velocity Vact, the actual front wheel side slip angleβf_act, and the actual rear wheel side slip angle βr_act, detected orestimated by the sensor/estimator 12. Then, based on these inputs, theFB distribution law 20 determines the virtual external forces Mvir, Fvirand the actuator operation FB target value.

Supplementally, the virtual external forces Mvir and Fvir correspond tothe vehicle model operation control inputs in the present invention, andthe actuator operation FB target value corresponds to the actual vehicleactuator operation control input in the present invention. Therefore,the FB distribution law 20 has a function as the model state amounterror response control means and the actual vehicle state amount errorresponse control means in the present invention.

Meanwhile, in parallel to the control processing (or by time-sharingprocessing) by the reference manipulated variable determiner 14, thereference dynamic characteristics model 16, the subtracter 18, and theFB distribution law 20 explained above, the controller 10 supplies theaforesaid drive operation inputs to an FF law 22 to determine anactuator operation FF target value, which is a feedforward target value(basic target value) of the operation of the actuator devices 3, by theFF law 22.

In the present embodiment, the actuator operation FF target valueincludes the feedforward target values related to the driving/brakingforces of the wheels W1 to W4 of the actual vehicle 1 by the operationof the braking device of the driving/braking device 3A, the feedforwardtarget values related to the driving/braking forces of the drivingwheels W1 and W2 of the actual vehicle 1 by the operation of the drivingsystem of the driving/braking device 3A, the feedforward target valuesrelated to the reduction gear ratio (change gear ratio) of thetransmission of the driving/braking device 3A, and the feedforwardtarget values related to the steering angles of the steering controlwheels W1 and W2 of the actual vehicle 1 by the steering device 3B.

To determine these actuator operation FF target values, the FF law 22receives the drive operation input and also receives the actual stateamount (the actual traveling velocity Vact or the like) detected orestimated by the sensor/estimator 12. Then, based on these inputs, theFF law 22 determines the actuator operation FF target value. Theactuator operation FF target value is an operation target value of theactuator devices 3 which is determined without depending on the stateamount errors γerr and βerr (the first state amount errors).

Supplementally, if the suspension device 3C is an active suspensiondevice, then the actuator operation FF target value generally includes afeedforward target value related to an operation of the suspensiondevice 3C.

Subsequently, the controller 10 inputs the actuator operation FF targetvalue (the current time value) determined by the FF law 22 and theactuator operation FB target value (the current time value) determinedby the FB distribution law 20 to the actuator operation target valuesynthesizer 24. Then, the controller 10 synthesizes the actuatoroperation FF target value and the actuator operation FB target value bythe actuator operation target value synthesizer 24 to determine theactuator operation target value, which is a target value defining theoperation of the actuator devices 3.

According to the present embodiment, the actuator operation targetvalues include a target value of the driving/braking forces of thewheels W1 to W4 of the actual vehicle 1 (a target value of the totaldriving/braking force by the operations of the driving system of thedriving/braking device 3A and the braking device), a target value of aslip ratio of the wheels W1 to W4 of the actual vehicle 1, a targetvalue of a steering angle of the steering control wheels W1 and W2 ofthe actual vehicle 1 by the steering device 3B, a target value of thedriving/braking force of the driving wheels W1 and W2 of the actualvehicle 1 by the operation of the driving system of the driving/brakingdevice 3A, and a target value of a reduction gear ratio of thetransmission of the driving/braking device 3A.

To determine these actuator operation target values, the actuatoroperation target value synthesizer 24 receives not only the actuatoroperation FF target value and the actuator operation FB target value butalso the actual state amounts (the actual side slip angle βf_act of thefront wheels W1, W2 and the estimated friction coefficient μestm, etc.)detected or estimated by the sensor/estimator 12. Then, based on theseinputs, the actuator operation target value synthesizer 24 determinesthe actuator operation target value.

Supplementally, the actuator operation target value is not limited tothe types of target values described above. For example, in place of thetarget values, the target values of the actuator manipulated variablesof the actuator devices 3 that are associated with the aforesaid targetvalues may be determined. Basically, the actuator operation targetvalues may take any values as long as they make it possible to definethe operations of the actuator devices. For instance, as the actuatoroperation target value related to an operation of the braking device,the target value of a braking pressure may be determined or the targetvalue of the actuator manipulated variable of the braking deviceassociated therewith may be determined.

Subsequently, the controller 10 inputs the actuator operation targetvalue, which has been determined by the actuator operation target valuesynthesizer 24, into the actuator drive control unit 26, and determinesthe actuator manipulated variable of each of the actuator devices 3 ofthe actual vehicle 1 by the actuator drive control unit 26. Then, theactuator of each of the actuator devices 3 of the actual vehicle 1 iscontrolled on the basis of the determined actuator manipulated variable.

In this case, the actuator drive control unit 26 determines the actuatormanipulated variable such that the input actuator operation target valueis satisfied or in exact accordance with the actuator operation targetvalue. Further, for this determination, the actuator drive control unit26 further receives the actual state amounts of the actual vehicle 1detected or estimated by the sensor/estimator 12 in addition to theactuator operation target value. Among the control functions of theactuator drive control unit 26, the control function related to thebraking device of the driving/braking device 3A desirably incorporates aso-called antilock braking system.

The above has provided an overview of the control processing for eachcontrol processing cycle of the controller 10.

The order of the processing of each control processing function sectionof the controller 10 may be changed, as necessary. For example, theprocessing by the sensor/estimator 12 may be executed at the end of eachcontrol processing cycle and a detected value or an estimated valueobtained thereby may be used for the processing of the next controlprocessing cycle.

More detailed processing of the control processing function section ofthe controller 10 in the present embodiment will now be explained.

[About a Reference Dynamic Characteristics Model]

First, the reference dynamic characteristics model 16 in the presentembodiment will be explained by referring to FIG. 3. FIG. 3 is a diagramshowing the construction of a vehicle on the reference dynamiccharacteristics model 16 in the present embodiment. This referencedynamic characteristics model 16 is a model which expresses the dynamiccharacteristics of a vehicle in terms of the dynamic characteristics(kinetic characteristics) on a horizontal plane of a vehicle equippedwith one front wheel Wf and one rear wheel Wr at the front and the back(a so-called two-wheeled model). Hereinafter, the vehicle on thereference dynamic characteristics model 16 (the vehicle corresponding tothe actual vehicle 1 on the reference dynamic characteristics model 16)will be referred to as the model vehicle. The front wheel Wf of themodel vehicle corresponds to a wheel that combines the two front wheelsW1 and W2 of the actual vehicle 1 into one piece and provides thesteering control wheel of the model vehicle. The rear wheel Wrcorresponds to a wheel that combines the rear wheels W3 and W4 of theactual vehicle 1 into one piece and provides a non-steering controlwheel in the present embodiment.

An angle βd formed with respect to the longitudinal direction of themodel vehicle by the velocity vector Vd on the horizontal plane of acenter-of-gravity point Gd of the model vehicle (i.e., a vehiclecenter-of-gravity point side slip angle βd of the model vehicle) and theangular velocity γd about the vertical axis of the model vehicle (i.e.,the yaw rate γd of the model vehicle) are the reference state amountssequentially determined by the reference dynamic characteristics model16 as the reference vehicle center-of-gravity point side slip angle andthe reference yaw rate, respectively. Further, an angle δf_d formed withrespect to the longitudinal direction of the model vehicle by a line ofintersection of the rotational plane of the front wheel Wf of the modelvehicle and the horizontal plane is the reference model manipulatedvariable input to the reference dynamic characteristics model 16 as themodel front wheel steering angle. Further, a translational force Fvir inthe lateral direction additionally applied to the center-of-gravitypoint Gd of the model vehicle (in the lateral direction of the modelvehicle) and a moment Mvir in the yaw direction (about the verticalaxis) additionally applied about the center-of-gravity point Gd of themodel vehicle are the feedback control inputs supplied as the virtualexternal forces to the reference dynamic characteristics model 16.

In FIG. 3, Vf_d denotes an advancing velocity vector of the front wheelWf of the model vehicle on the horizontal plane, Vr_d denotes anadvancing velocity vector of the rear wheel Wr of the model vehicle onthe horizontal plane, βf_d denotes a side slip angle of the front wheelWf (an angle formed with respect to the longitudinal direction of thefront wheel Wf (the direction of the line of intersection of therotational plane of the front wheel Wf and the horizontal plane) by theadvancing velocity vector Vf_d of the front wheel Wf. Hereinafterreferred to as the front wheel side slip angle βf_d), βr_d denotes aside slip angle of the rear wheel Wr (an angle formed with respect tothe longitudinal direction of the rear wheel Wr (the direction of theline of intersection of the rotational plane of the rear wheel Wr andthe horizontal plane) by the advancing velocity vector Vr_d of the rearwheel Wr. Hereinafter referred to as the rear wheel side slip angleβr_d), and βf0 denotes an angle formed with respect to the longitudinaldirection of the model vehicle by the advancing velocity vector Vf_d ofthe front wheel Wf of the model vehicle (hereinafter referred to as thevehicle front wheel position side slip angle).

Supplementally, according to the embodiments in the present description,regarding a side slip angle of a vehicle or a wheel, a steering angle ofa wheel, a yaw rate of the vehicle and a moment in the yaw direction,the counterclockwise direction as observed from above the vehicle isdefined as the positive direction. Further, of the virtual externalforces Mvir and Fvir, the translational force Fvir defines the leftwarddirection of the vehicle as the positive direction. For adriving/braking force of a wheel, the direction of a force foraccelerating the vehicle forward in the direction of the line ofintersection of the rotational plane of a wheel and a road surface or ahorizontal plane (road surface reaction force) is defined as thepositive direction. In other words, a driving/braking force in thedirection that provides a driving force relative to the advancingdirection of the vehicle takes a positive value, while a driving/brakingforce in the direction that provides a braking force relative to theadvancing direction of the vehicle takes a negative value.

Specifically, the dynamic characteristics (the dynamic characteristicsin a continuous system) of the model vehicle are represented byexpression 01 given below. The formula excluding the third term (theterm including Fvir and Mvir) of the right side of this expression 01 isequivalent to, for example, the publicly known expressions (3.12),(3.13) shown in the publicly known document titled “Motion and Controlof Automobile” (written by Masato Abe; published by Sankaido Co., Ltd.;and 2nd printing, 2nd edition published on Jul. 23, 2004: hereinafterreferred to as non-patent document 1).

$\begin{matrix}\lbrack {{Mathematical}\mspace{14mu} {Expression}\mspace{14mu} 1} \rbrack & \; \\{{\frac{\;}{t}\begin{bmatrix}{\beta \; d} \\{\gamma \; d}\end{bmatrix}} = {\begin{bmatrix}{a\; 11} & {a\; 12} \\{a\; 21} & {a\; 22}\end{bmatrix} \cdot {\quad{{\begin{bmatrix}{\beta \; d} \\{\gamma \; d}\end{bmatrix} + {{\begin{bmatrix}{b\; 1} \\{b\; 2}\end{bmatrix} \cdot \delta}\; {f\_ d}} + {{\begin{bmatrix}{b\; 11} & 0 \\0 & {b\; 22}\end{bmatrix} \cdot \begin{bmatrix}{F\; {vir}} \\{M\; {vir}}\end{bmatrix}}{where}{a\; 11}}} = {{{- \frac{2 \cdot ( {{Kf} + {Kr}} )}{m \cdot {Vd}}}{a\; 12}} = {{{- \frac{{m \cdot {Vd}^{2}} + {2 \cdot ( {{{Lf} \cdot {Kf}} - {{Lr} \cdot {Kr}}} )}}{m \cdot {Vd}^{2}}}{a\; 21}} = {{{- \frac{2 \cdot ( {{{Lf} \cdot {Kf}} - {{Lr} \cdot {Kr}}} )}{I}}{a\; 22}} = {{{- \frac{2 \cdot ( {{{Lf}^{2} \cdot {Kf}} + {{Lr}^{2} \cdot {Kr}}} )}{I \cdot {Vd}}}{b\; 1}} = {{\frac{2 \cdot {Kf}}{m \cdot {Vd}}{b\; 2}} = {{\frac{2 \cdot {Lf} \cdot {Kf}}{I}\; {b\; 11}} = {{\frac{1}{m \cdot {Vd}}b\; 22} = \frac{1}{I}}}}}}}}}}}} & {{Expression}\mspace{14mu} 01}\end{matrix}$

In the note of the expression 01, m denotes the total mass of the modelvehicle, Kf denotes the cornering power per wheel when the front wheelWf of the model vehicle is regarded as a connected body of the two rightand left front wheels, Kr denotes the cornering power per wheel when therear wheel Wr of the model vehicle is regarded as a connected body ofthe two right and left rear wheels, Lf denotes the distance in thelongitudinal direction between the center of the front wheel Wf of themodel vehicle and the center-of-gravity point Gd (the distance in thelongitudinal direction between the rotational axis of the front wheel Wfand the center-of-gravity point Gd when the steering angle of the frontwheel Wf is zero. Refer to FIG. 3), Lr denotes the distance in thelongitudinal direction between the center of the rear wheel Wr of themodel vehicle and the center-of-gravity point Gd (the distance in thelongitudinal direction between the rotational axis of the rear wheel Wrand the center-of-gravity point Gd. Refer to FIG. 3), and I denotes theinertia (inertial moment) about the yaw axis at the center-of-gravitypoint Gd of the model vehicle. These parameter values are preset values.In this case, for example, m, I, Lf and Lr are set to the same orsubstantially the same values thereof in the actual vehicle 1. Further,Kf and Kr are set by considering the characteristics of the tires (orthe characteristics required of the tires) of the front wheels W1, W2and the rear wheels W3, W4, respectively, of the actual vehicle 1.Depending on the setting of the values of Kf and Kr (more generally, thevalues of a11, a12, a21, and a22), the steering characteristics, such asunder-steering, over-steering, and neutral steering, can be set.Further, the values of m, I, Kf, and Kr in the actual vehicle 1 may beidentified during a travel of the actual vehicle 1 and the identifiedvalues may be used as the values of m, I, Kf, and Kr of the modelvehicle.

Supplementally, the relationship among βf0, βd, βf_d, βr_d, γd, and δf_dof the model vehicle is represented by expressions 02a, 02b, and 02cgiven below.

βf _(—) d=βd+Lf·γd/Vd−δf _(—) d   Expression 02a

βr _(—) d=βd−Lr·γd/Vd   Expression 02b

βf0=βf _(—) d+δf _(—) d=βd+Lf·γd/Vd   Expression 02c

Further, as shown in FIG. 3, if the cornering force of the front wheelWf of the model vehicle (≈a lateral force of the front wheel Wf) isdenoted by Ffy_d and the cornering force of the rear wheel Wr of themodel vehicle (≈a lateral force of the rear wheel Wr) is denoted byFry_d, then the relationship between Ffy_d and βf_d and the relationshipbetween Fry_d and βr_d are represented by expressions 03a and 03b shownbelow.

Ffy _(—) d=−2·Kf·βf _(—) d   Expression 03a

Fry _(—) d=−2·Kr·βr _(—) d   Expression 03b

In the processing by the reference dynamic characteristics model 16 inthe present embodiment, δf_d, Fvir, and Mvir in expression 01 givenabove are used as inputs and the arithmetic processing of expression 01(specifically, the arithmetic processing of an expression obtained byrepresenting expression 01 in terms of a discrete-time system) issequentially carried out at a control processing cycle of the controller10, thereby sequentially calculating βd and γd in a time series manner.In this case, at each control processing cycle, a latest value (acurrent time value) of the actual traveling velocity Vact detected orestimated by the sensor/estimator 12 is used as the value of thetraveling velocity Vd of the model vehicle. In other words, thetraveling velocity Vd of the model vehicle is always made to agree withthe actual traveling velocity Vact. As the values of Fvir and Mvir, thelatest values (last time values) of the virtual external forcesdetermined as will be discussed later by the FB distribution law 20 areused. As the value of δf_d, a latest value (a current time value) of amodel front wheel steering angle determined as will be discussed by thereference manipulated variable determiner 14 is used. In addition, thelast time values of βd and γd are also used to calculate new βd and γd(current time values).

Supplementally, the dynamic characteristics of the model vehicle may,more generally, be represented by expression (4) shown below.

$\begin{matrix}\lbrack {{Mathematical}\mspace{14mu} {expression}{\mspace{11mu} \;}2} \rbrack & \; \\{{\frac{}{t}\begin{bmatrix}{\beta \; d} \\{\gamma \; d}\end{bmatrix}} = {\begin{bmatrix}{f\; 1( {{\gamma \; d},{\beta \; d},{\delta \; {f\_ d}}} )} \\{f\; 2( {{\gamma \; d},{\beta \; d},{\delta \; {f\_ d}}} )}\end{bmatrix} + {\begin{bmatrix}{b\; 11} & 0 \\0 & {b\; 22}\end{bmatrix} \cdot \begin{bmatrix}{F\; {vir}} \\{M\; {vir}}\end{bmatrix}}}} & {{Expression}\mspace{14mu} 04}\end{matrix}$

wherein f1(γd, βd, δf_d) and f2(γd, βd, δf_d) are functions of γd, βd,and δf_d, respectively. The above expression 01 is an example of thecase where the values of the functions f1 and f2 are represented interms of linear coupling (primary coupling) of γd, βd, and δf_d. Thefunctions f1 and f2 do not have to be the functions represented bymathematical expressions, and the function values thereof may befunctions determined by a map from the values of γd, βd, and δf_d.

The behavior characteristics of the actual vehicle 1 in the presentembodiment show behavior characteristics somewhere between the opencharacteristics of the actual vehicle 1 when the present invention isnot applied (the behavior characteristics of the actual vehicle 1 whenthe actuator FB operation target value is steadily maintained at zero)and the behavior characteristics of the reference dynamiccharacteristics model 16 when the virtual external forces Mvir and Fvirare steadily maintained at zero. Therefore, in general, the referencedynamic characteristics model 16 is desirably set to a model that showsa response behavior which a driver considers more preferable than theopen characteristics of the actual vehicle 1. To be more specific, thereference dynamic characteristics model 16 is desirably set to be amodel having higher linearity than that in the actual vehicle 1. Forexample, it is desirable to set the reference dynamic characteristicsmodel 16 such that the relationship between the side slip angle or theslip ratio of a wheel of the model vehicle and a road surface reactionforce acting on the wheel from the road surface (a lateral force or adriving/braking force) is a linear relationship or a relationship closethereto. The reference dynamic characteristics model 16 representingdynamic characteristics by the expression 01 is one example of the modelthat satisfies these requirements.

However, the reference dynamic characteristics model 16 may have acharacteristic in which a road surface reaction force acting on thewheels Wf and Wr of the model vehicle saturates in response to a changein a side slip angle or a slip ratio. For instance, the values of thecornering powers Kf and Kr are set on the basis of the front wheel sideslip angle βf_d and the rear wheel side slip angle βr_d rather thansetting them at constant values. And, at this time, the value of Kf isset on the basis of βf_d such that the lateral force Ffy_d of the frontwheel Wf generated on the basis of βf_d (refer to the expression 03a)saturates as βf_d increases when the absolute value of the front wheelside slip angle βf_d has increased to a certain degree. Similarly, thevalue of Kr is set on the basis of βr_d such that the lateral forceFry_d of the rear wheel Wr generated on the basis of βr_d (refer to theexpression 03b) saturates as βr_d increases when the absolute value ofthe rear wheel side slip angle βr_d has increased to a certain degree.This causes the lateral forces Ffy_d and Fry_d acting on the wheels Wfand Wr of the model vehicle to have the saturation characteristicrelative to the side slip angle βf_d or βr_d.

[About the Reference Manipulated Variable Determiner]

The details of the processing by the reference manipulated variabledeterminer 14 will now be explained with reference to FIG. 4 and FIG. 5.FIG. 4 is a functional block diagram showing the details of theprocessing function of the reference manipulated variable determiner 14,and FIG. 5 is a graph for explaining the processing by an excessivecentrifugal force prevention limiter 14 f provided in the referencemanipulated variable determiner 14.

Referring to FIG. 4, the reference manipulated variable determiner 14first determines, in a processor 14 a, an unlimited front wheel steeringangle δf_unltd by dividing a steering angle θh (a current time value) inthe drive operation inputs, which are to be supplied, by an overallsteering ratio_(is). This unlimited front wheel steering angle δf_unltdhas a meaning as a basic required value of a model front wheel steeringangle δf_d based on the steering angle θh.

The overall steering ratio “is” is the ratio between the steering angleθh and the steering angle of the front wheel Wf of the model vehicle,and it is set in conformity with, for example, the relationship betweenthe steering angle θh of the actual vehicle 1 and the feedforward valueof the steering angle of the front wheels W1 and W2 of the actualvehicle 1 associated therewith.

The overall steering ratio “is” may be variably set on the basis of thetraveling velocity Vact of the actual vehicle 1 detected or estimated bythe sensor/estimator 12 rather than setting it at a constant value (afixed value). In this case, it is desirable to set the “is” such thatthe overall steering ratio “is” increases as the traveling velocity Vactof the actual vehicle 1 increases.

Subsequently, the vehicle front wheel position side slip angle βf0 ofthe model vehicle on the reference dynamic characteristics model 16 isdetermined by a βf0 calculator 14 b. The βf0 calculator 14 b receivesthe last time values of the reference yaw rate γd and the referencevehicle center-of-gravity point side slip angle βd determined by thereference dynamic characteristics model 16. From these values, the lasttime value of βf0 is determined by calculating the expression 02c(calculating the right side of the second equal sign of expression 02c)Thus, βf0 calculated by the βf0 calculator 14 b takes the value of thevehicle front wheel position side slip angle βf0 of the model vehicle atthe last time control processing cycle.

Alternatively, the last time value of the front wheel side slip angleβf_d of the model vehicle may be determined by the calculation of theexpression 02a from the last time values of γd and βd, the last timevalue of the model front wheel steering angle δf_d determined by thereference manipulated variable determiner 14, and the last time value ofthe actual traveling velocity Vact, then the last time value of themodel front wheel steering angle δf_d determined by the referencemanipulated variable determiner 14 may be added to the determined βf_d(calculating the right side of the first equal sign of expression 02c)thereby to determine βf0. Alternatively, at each control processingcycle, the calculation of βf0 may be carried out by the processingperformed by the reference dynamic characteristics model 16, and thelast time value of the calculated βf0 may be input to the referencemanipulated variable determiner 14. In this case, the arithmeticprocessing by the βf0 calculator 14 b in the reference manipulatedvariable determiner 14 is unnecessary.

Subsequently, the unlimited front wheel steering angle δf_unltd issubtracted by a subtracter 14 c from the vehicle front wheel positionside slip angle βf0 determined as described above, thereby determiningthe unlimited front wheel side slip angle. The unlimited front wheelside slip angle means an instantaneous predicted value of the frontwheel side slip angle βf_d of the model vehicle generated if it isassumed that the model front wheel steering angle δf_d of the modelvehicle is instantaneously controlled to the unlimited front wheelsteering angle δf_unltd (current time value) from the last time value.

Subsequently, the reference manipulated variable determiner 14 passesthe unlimited front wheel side slip angle through a front wheel sideslip angle limiter 14 d to determine a limited front wheel side slipangle. The graph of the front wheel side slip angle limiter 14 d shownin the figure is a graph illustrating the relationship between anunlimited front wheel side slip angle and a limited front wheel sideslip angle, the values in the direction of the axis of abscissas relatedto the graph indicating the values of the unlimited front wheel sideslip angles while the values in the direction of the axis of ordinatesindicating the values of the limited front wheel side slip angles.

The front wheel side slip angle limiter 14 d is a limiter forrestraining the magnitude of the front wheel side slip angle βf_d of themodel vehicle from becoming excessive (furthermore, for preventing thelateral forces of the front wheels W1 and W2 required for the actualvehicle 1 from becoming excessive).

In the present embodiment, the front wheel side slip angle limiter 14 dsets the permissible range of the front wheel side slip angle βf_d (morespecifically, the upper limit value βf_max(>0) and the lower limit valueβf_min(<0) of the permissible range) on the basis of the estimatedfriction coefficient μestm (current time value) and the actual travelingvelocity Vact (current time value) input from the sensor/estimator 12into the reference manipulated variable determiner 14. In this case,basically, the permissible range is set such that the permissible range[βf_min, βf_max] is narrower (βf_max and βf_min are brought more closelyto zero) as the estimated friction coefficient μestm is smaller or theactual traveling velocity Vact is higher. At this time, the permissiblerange [βf_min, βf_max] is set in the range of the values of side slipangle that maintains the relationship between, for example, the sideslip angle and the lateral force of the front wheels W1 and W2 of theactual vehicle 1 or the cornering force at a substantially linearrelationship (a proportional relationship).

The permissible range [βf_min, βf_max] may be set on the basis of eitherμestm or Vact, or may be set to a pre-fixed permissible rangeindependently of μestm and Vact.

And, if the value of the received unlimited front wheel side slip angleis within the permissible range [f_min, βf_max] set as described above(if βf_min≦unlimited front wheel side slip angle≦βf_max), then the frontwheel side slip angle limiter 14 d directly outputs the value of theunlimited front wheel side slip angle as the limited front wheel sideslip angle. If the value of the received unlimited front wheel side slipangle deviates from the permissible range, then the front wheel sideslip angle limiter 14 d outputs the lower limit value βf_min or theupper limit value βf_max of the permissible range [βf_min, βf_max] asthe limited front wheel side slip angle. To be more specific, if theunlimited front wheel side slip angle>βf_max, then the βf_max is outputas the limited front wheel side slip angle. If the unlimited front wheelside slip angle<βf_min, then the βf_min is output as the limited frontwheel side slip angle. Thus, the limited front wheel side slip angle isdetermined such that it agrees with an unlimited front wheel side slipangle or takes a value that is closest to the unlimited front wheel sideslip angle within the permissible range [βf_min, βf_max].

Subsequently, the limited front wheel side slip angle determined asdescribed above is subtracted by a subtracter 14 e from the vehiclefront wheel position side slip angle βf0 determined by the βf0calculator 14 b thereby to determine a first limited front wheelsteering angle δf_ltd1. The first limited front wheel steering angleδf_ltd1 determined as described above has a meaning as a model frontwheel steering angle δf_d obtained by restricting the unlimited frontwheel steering angle δf_unltd such that the front wheel side slip angleβf_d of the model vehicle does not deviate from the permissible range[βf_min, βf_max].

Subsequently, the reference manipulated variable determiner 14 passesthe first limited front wheel steering angle δf_ltd1 through theexcessive centrifugal force prevention limiter 14 f to determine asecond limited front wheel steering angle δf_ltd2. This δf_ltd2 is usedas the value of the model front wheel steering angle δf_d to be input tothe reference dynamic characteristics model 16. The graph of theexcessive centrifugal force prevention limiter 14 f shown in the figureis a graph illustrating the relationship between the first limited frontwheel steering angle δf_ltd1 and the second limited front wheel steeringangle δf_ltd2, the values in the direction of the axis of abscissasrelated to the graph indicating the values of δf_ltd1 while the valuesin the direction of the axis of ordinates indicating the values ofδf_ltd2.

The excessive centrifugal force prevention limiter 14 f is a limiter forrestraining the centrifugal force generated in the model vehicle frombecoming excessive (furthermore, for preventing the centrifugal forcerequired for the actual vehicle 1 from becoming excessive).

In the present embodiment, the excessive centrifugal force preventionlimiter 14 f sets the permissible range of the model front wheelsteering angle δf_d (more specifically, the upper limit value δf_max(>0)and the lower limit value δf_min(<0) of the permissible range) on thebasis of the estimated friction coefficient μestm (current time value)and the actual traveling velocity Vact (current time value) input to thereference manipulated variable determiner 14. This permissible range[δf_min, δf_max] is the permissible range of the model front wheelsteering angle δf_d that allows the model vehicle to make a normalcircular turn without exceeding the limit of friction against a roadsurface when the virtual external forces Mvir and Fvir are steadily heldat zero.

More specifically, first, a maximum yaw rate γmax (>0) at a normalcircular turn, which is a yaw rate that satisfies expression 05 givenbelow, is determined on the basis of the values (current time values) ofVact and μestm input to the reference manipulated variable determiner14.

m·γmax·Vact=C1·μestm·m·g   Expression 05

where m in expression 05 denotes the total mass of the model vehicle, asdescribed above. Further, g denotes a gravitational acceleration and C1denotes a positive coefficient of 1 or less. The left side of thisexpression 05 means a centrifugal force generated in the model vehicle(more specifically, a predicted convergence value of the centrifugalforce) when the normal circular turn of the model vehicle is made whileholding the yaw rate γd and the traveling velocity Vd of the modelvehicle at γmax and Vact, respectively. Further, the value of thecomputation result of the right side of expression 05 indicates thevalue (≦the limit value) obtained by multiplying the limit value of themagnitude of a road surface reaction force determined on the basis ofμestm (more specifically, a total frictional force that can be appliedto the model vehicle from a road surface through the intermediary of thewheels Wf and Wr (the total sum of the translational force horizontalcomponents of a road surface reaction force)) by the coefficient C1.Hence, the maximum yaw rate γmax at a normal circular turn is determinedsuch that the centrifugal force generated in the model vehicle when thenormal circular turn of the model vehicle is made while holding thevirtual external forces Mvir and Fvir to be applied to the model vehicleat zero and holding the yaw rate γd and the traveling velocity Vd of themodel vehicle at γmax and Vact, respectively, does not exceed the limitvalue of the total frictional force (the total sum of the translationalforce horizontal components of a road surface reaction force) which canbe applied to the model vehicle on the basis of the estimated frictioncoefficient μestm.

Incidentally, the value of the coefficient C1 of expression 05 may bevariably set on the basis of at least either one of μestm and Vact. Inthis case, preferably, the value of C1 is set to be smaller as μestm issmaller or as Vact is higher.

Subsequently, the value of the model front wheel steering angle δf_dassociated with γmax at the normal circular turn of the model vehicle isdetermined as a limit steering angle at normal circular turnδf_max_c(>0). In the reference dynamic characteristics model 16represented by the expression 01, the relationship of expression 06given below holds between the yaw rate γd of the model vehicle at thenormal circular turn and the model front wheel steering angle δf_d.

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu} \;}{expression}{\mspace{11mu} \;}3} \rbrack & \; \\{{{\gamma \; d} = {{\frac{1}{1 - {\frac{m}{2 \cdot L^{2}} \cdot \frac{{{Lf} \cdot {Kf}} - {{Lr} \cdot {Kr}}}{{Kf} \cdot {Kr}} \cdot {Vd}^{2}}} \cdot \frac{Vd}{L} \cdot \delta}\; {f\_ d}}}{{{where}\mspace{14mu} L} = {{Lf} + {Lr}}}} & {{Expression}{\mspace{11mu} \;}06}\end{matrix}$

If Vd is sufficiently small (if it is possible to regard as Vd²≈0), thenexpression 06 can be approximately rewritten to the following expression07.

γd=(Vd/L)·δf _(—) d   Expression 07

Hence, in the present embodiment, the limit steering angle δf_max_c atnormal circular turn associated with γmax is determined by making asolution on δf_d by taking the values of γd and Vd, respectively, inexpression 06 or expression 07 as γmax and Vact.

The permissible range [δf_min, δf_max] of the model front wheel steeringangle δf_d for preventing a centrifugal force generated in the modelvehicle from becoming excessive may be basically set to a permissiblerange [−δf_max_c, δf_max_c]. In that case, however, the model frontwheel steering angle δf_d may be subjected to unwanted restriction in acountersteering state of the actual vehicle 1 (a state wherein the frontwheels W1 and W2 are steered in the direction of the opposite polarityfrom the polarity of the yaw rate of the actual vehicle 1).

In the present embodiment, therefore, δf_max_c and −δf_max_c arecorrected according to expressions 08a and 08b given below on the basisof the yaw rates γd and γmax of the model vehicle thereby to set theupper limit value δf_max and the lower limit value δf_min of thepermissible range of the model front wheel steering angle δf_d.

δf_max=δf_max_(—) c+fe(γd, γmax)   Expression 08a

δf_min=−δf_max_(—) c−fe(−γd, −γmax)   Expression 08b

fe(γd, γmax) and fe(−γd, −γmax) in expressions 08a and 08b are functionsof γd and γmax, and the function values thereof are, for example,functions that vary according to the values of γd and γmax, as shown inthe graphs of FIGS. 5( a) and (b). In this example, the value of thefunction fe(γd, γmax) takes a positive fixed value fex if γd takes avalue of a predetermined value γ1, which is slightly larger than zero,or less (including a case where γd<0), as shown in the graph of FIG. 5(a). And, the value of fe(γd, γmax) monotonously decreases as γdincreases if γd>γ1 and reaches zero by the time γd reaches γ2(>γ1),which is a predetermined value of γmax or less. Further, the value offe(γd, γmax) is maintained at zero if γd>γ2 (including the case whereγd≧γmax).

Further, a function fe(−γd, −γmax) is a function obtained by reversingthe polarities of the variables γd and γmax of the function fe(γd,γmax), so that the value of the function fe(−γd, −γmax) varies inrelation to γd, as shown in the graph of FIG. 5( b). More specifically,if γd takes a value of a predetermined negative value −γ1, which isslightly smaller than zero, or more (including the case where γd>0),then the function takes a positive fixed value fex. And, the value offe(−γd, −γmax) monotonously decreases as γd decreases if γd<−γ1 andreaches zero by the time when γd reaches −γ2, which is a predeterminedvalue of −γmax or more. Further, the value of fe(−γd, −γmax) ismaintained at zero if γd<−γ2 (including the case where γd≦−γmax).

As the value of γd required for determining the values of the functionsfe(γd, γmax) and fe(−γd, −γmax), the last time value of the referenceyaw rate γd determined by the reference dynamic characteristics model 16may be used.

Further, the values γ1 and γ2 of γd at breakpoints of the graph of thefunction fe(γd, γmax) or the aforesaid positive fixed value fex may bevariably changed according to the estimated friction coefficient μestmor the actual traveling velocity Vact.

The permissible range [δf_min, δf_max] of the model front wheel steeringangle δf_d is set by correcting δf_max_c on the basis of the value ofthe function fe as described above, so that the magnitude (the absolutevalue) of the limit value δf_max or δf_min of the model front wheelsteering angle δf_d in the direction opposite from the direction of γdis set to be larger than the limit steering angle δf_max_c at a normalcircular turn associated with the limit of a centrifugal force generatedin the model vehicle. This makes it possible to prevent the model frontwheel steering angle δf_d from being subjected to unwanted restrictionin the countersteering state of the actual vehicle 1. Incidentally, thepermissible range [−δf_min, δf_max] narrows as the actual travelingvelocity Vact increases or as the estimated friction coefficient μestmdecreases.

After setting the permissible range of the model front wheel steeringangle δf_d as described above, the excessive centrifugal forceprevention limiter 14 f directly outputs the value of δf_ltd1 as thesecond limited front wheel steering angle δf_ltd2 (=the model frontwheel steering angle δf_d to be input to the reference dynamiccharacteristics model 16) if the received first limited front wheelsteering angle δf_ltd1 takes a value within the permissible range[δf_min, δf_max] (if δf_min≦δf_ltd1≦δf_max). Further, if the value ofthe received δf_ltd1 deviates from the permissible range [δf_min,δf_max], then the excessive centrifugal force prevention limiter 14 foutputs a value obtained by forcibly restricting the input value as thesecond limited front wheel steering angle δf_ltd2. To be more specific,if δf_ltd1>δf_max, then δf_max is output as the second limited frontwheel steering angle δf_ltd_2, and if δf_ltd1<δf_min, then δf_min isoutput as the second limited front wheel steering angle δf_ltd2. Thus,δf_ltd2 is determined such that it agrees with the first limited frontwheel steering angle δf_ltd1 or takes a value that is closest to thefirst limited front wheel steering angle δf_ltd1 within the permissiblerange [δf_min, δf_max].

In the reference dynamic characteristics model 16 represented by theexpression 01, the relationship of expression 09 given below holdsbetween βd and γd at a normal circular turn of the model vehicle.

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu} \;}{expression}\mspace{14mu} 4} \rbrack & \; \\{{\beta \; d} = {{( {1 - {\frac{m}{2 \cdot L} \cdot \frac{Lf}{{Lr} \cdot {Kr}} \cdot {Vd}^{2}}} ) \cdot \frac{Lr}{Vd} \cdot \gamma}\; d}} & {{Expression}\mspace{14mu} 09}\end{matrix}$

If Vd is sufficiently small (if it is possible to regard as Vd²≈0), thenexpression 09 can be approximately rewritten to the following expression10.

βd=(Lr/Vd)·γd   Expression 10

Hence, the value of γd or γmax at the normal circular turn of the modelvehicle can be converted into a value of βd (provided Vd=Vact) accordingto expression 09 or expression 10. Therefore, the permissible range ofthe model front wheel steering angle δf_d may be set on the basis of thevalue of the vehicle center-of-gravity point side slip angle βdassociated with the yaw rates γd and γmax instead of setting thepermissible range of the model front wheel steering angle δf_d on thebasis of the values of the yaw rates γd and γmax as described above.

The above has presented the details of the processing by the referencemanipulated variable determiner 14.

The processing by the reference manipulated variable determiner 14explained above determines, at each control processing cycle, the secondlimited front wheel steering angle δf_ltd2 as the model front wheelsteering angle δf_d to be input to the reference dynamic characteristicsmodel 16 on the basis of the steering angle θh among drive operationinputs such that an instantaneous value of the front wheel side slipangle βf_d of the model vehicle on the reference dynamic characteristicsmodel 16 does not become excessive and the centrifugal force generatedin the model vehicle does not become excessive.

Supplementally, in the excessive centrifugal force prevention limiter 14f, limiting the model front wheel steering angle δf_d to be input to thereference dynamic characteristics model 16 as described above to preventthe centrifugal force generated in the model vehicle from becomingexcessive is equivalent to limiting the model front wheel steering angleδf_d to prevent the vehicle center-of-gravity point side slip angle βd(or the rear wheel side slip angle βr_d) of the model vehicle frombecoming excessive. Further, in general, a centrifugal force in thevehicle or a vehicle center-of-gravity point side slip angle (or a rearwheel side slip angle) is generated with a delay from a steeringoperation, so that the processing for limiting the model front wheelsteering angle δf_d performed by the excessive centrifugal forceprevention limiter 14 f may be said to be the processing for limitingthe model front wheel steering angle δf_d on the basis of a predictedconvergence value of a centrifugal force of the vehicle or a vehiclecenter-of-gravity point side slip angle (or a rear wheel side slipangle). In contrast to this, the limiting processing by the front wheelside slip angle limiter 14 d may be said to be the processing forlimiting the model front wheel steering angle δf_d to prevent aninstantaneous value of the front wheel side slip angle βf_d of the modelvehicle from becoming excessive.

In the present embodiment, the function fe used to set the permissiblerange [δf_min, δf_max] by the excessive centrifugal force preventionlimiter 14 f has been set as shown in FIGS. 5( a) and (b) describedabove; however, it is not limited thereto.

For instance, the function fe(γd, γmax) may be set as shown by thesolid-line graph in FIG. 6. In this example, the value of fe(γd, γmax)monotonously decreases as the value of γd increases (increases from avalue on the negative side to a value on the positive side) and becomeszero when γd=γmax. At this time, the function fe(−γd, −γmax) will be asindicated by the dashed-line graph in FIG. 6. In this case, the upperlimit value δf_max of the permissible range of the model front wheelsteering angle δf_d determined by the expression 08a will be closer tozero than the limit steering angle δf_max_c at normal circular turn asγd increases when γd exceeds γmax. Similarly, the lower limit valueδf_min of the permissible range of the model front wheel steering angleδf_d determined by the expression 08b will be closer to zero than−δf_max as γd decreases (as the magnitude increases) when γd exceeds−γmax onto the negative side.

Further, instead of the expressions 08a and 08b, the followingexpressions 11a and 11b may be used to set the upper limit value δf_maxand the lower limit value δf_min of the permissible range of δf_d, andthe functions fe(γd, γmax) and fe(−γd, −γmax) may be set as indicatedby, for example, the solid-line and dashed-line graphs in FIG. 7.

δf_max=δf_max_(—) c·fe(γd, γmax)   Expression 11a

δf_min=−δf_max_(—) c·fe(−γd, −γmax)   Expression 11b

In this example, the values of fe(γd, γmax) and fe(−γd, −γmax) arealways 1 or more and change with γd in the same manner as those shown inFIGS. 5( a) and (b). Then, these values of fe(γd, γmax) and fe(−γd,−γmax) are multiplied by δf_max_c and δf_min_c, respectively, to set theupper limit value δf_max and the lower limit value δf_min.

Further, the second limited front wheel steering angle δf_ltd2 may bedetermined by, for example, the processing described below in place ofsetting the permissible range [δf_min, δf_max] of the model front wheelsteering angle δf_d by correcting δf_max_c on the basis of a value ofthe function fe. FIG. 8 is a functional block diagram for explaining theprocessing function.

A front wheel steering angle correction Δδf for correcting the firstlimited front wheel steering angle δf_ltd1 determined by the front wheelside slip angle limiter 14 d is determined on the basis of the yaw rateγd (last time value) of the model vehicle in a processor 14 g. At thistime, Δδf is basically determined such that the value of Δδfmonotonously increases on the positive side as γd increases on thepositive side, while the value of Δδf monotonously decreases on thenegative side as γd decreases on the negative side, as shown by thegraph in the processor 14 g. In the graph in the processor 14 g, thevalue of Δδf is provided with an upper limit value (>0) and a lowerlimit value (<0). In this case, the upper limit value and the lowerlimit value are set such that, for example, the absolute values thereofare the same values as the fixed values fex shown in FIGS. 5( a) and (b)described above.

Subsequently, the front wheel steering angle correction Δδf determinedas described above is added by an adder 14 h to the first limited frontwheel steering angle δf_ltd1 calculated by the subtracter 14 e (refer toFIG. 4) thereby to determine a first limited front wheel steering anglewith input correction. In this case, if the direction of δf_ltd1 and thedirection of γd are opposite from each other, then the magnitude of thefirst limited front wheel steering angle with input correction will besmaller than the magnitude of δf_ltd1. However, if the direction ofδf_ltd1 and the direction of γd are the same, then the magnitude of thefirst limited front wheel steering angle with input correction will belarger than the magnitude of δf_ltd1.

Subsequently, the first limited front wheel steering angle with inputcorrection is passed through the excessive centrifugal force preventionlimiter 14 f to determine a second limited front wheel steering anglewith input correction obtained by restricting the first limited frontwheel steering angle with input correction to a value within thepermissible range [δf_min, δf_max] of the model front wheel steeringangle δf_d. In other words, if the first limited front wheel steeringangle with input correction has a value within the permissible range,then the first limited front wheel steering angle with input correctionis directly determined as the second limited front wheel steering anglewith input correction. Further, if the first limited front wheelsteering angle with input correction deviates from the permissiblerange, then either one of δf_max and δf_min which has a value closer tothe first limited front wheel steering angle with input correction isdetermined as the second limited front wheel steering angle with inputcorrection.

In this case, the upper limit value δf_max(>0) of the permissible rangeof the model front wheel steering angle δf_d in the excessivecentrifugal force prevention limiter 14 f is set to a value that isslightly larger than the steering angle limit value at normal circularturn δf_max_c (e.g., δf_max_c+fex), by taking into account thecorrection of δf_ltd1 when the direction of δf_ltd1 and the direction ofγd are the same. Similarly, the lower limit value δf_min(<0) of thepermissible range of the model front wheel steering angle δf_d is setsuch that the absolute value thereof will be a value that is slightlylarger than δf_max_c.

Subsequently, the front wheel steering angle correction Δδf issubtracted by a subtracter 14 i from the second limited front wheelsteering angle with input correction determined as described above,thereby determining the second limited front wheel steering angleδf_ltd2.

The model front wheel steering angle δf_d(=δf_ltd2) to be input to thereference dynamic characteristics model 16 can be determined whilepreventing the centrifugal force generated in the model vehicle frombecoming excessive and also preventing unwanted restriction from beingplaced in the countersteering state of the actual vehicle 1 even whenthe second limited front wheel steering angle δf_ltd2 is determined asdescribed above.

In the present embodiment, the processing by the front wheel side slipangle limiter 14 d and the excessive centrifugal force preventionlimiter 14 f has been carried out to determine the model front wheelsteering angle δf_d to be input to the reference dynamic characteristicsmodel 16; however, the processing by one or both of them may be omitted.More specifically, the unlimited front wheel steering angle δf_unltddetermined by the processor 14 a or a value obtained by supplying theδf_unltd to the excessive centrifugal force prevention limiter 14 f orthe first limited front wheel steering angle δf_ltd1 determined by thesubtracter 14 e may be determined as the model front wheel steeringangle δf_d to be input to the reference dynamic characteristics model16.

The current time value of the model front wheel steering angle δf_d(=the current time value of δf_ltd2) determined by the referencemanipulated variable determiner 14 as explained above is input to thereference dynamic characteristics model 16, and the current time valuesof the reference yaw rate γd and the reference vehicle center-of-gravitypoint side slip angle βd are newly determined by the reference dynamiccharacteristics model 16 (according to the expression 01) from the aboveinput value and the virtual external forces Fvir and Mvir (last timevalues) determined by the FB distribution law 20, as will be discussedlater. This processing is actually carried out according to anexpression obtained by representing expression 01 in terms of adiscrete-time system, so that the last time values of γd and βd are alsoused to determine the current time values of γd and βd.

In this case, the model front wheel steering angle δf_d input to thereference dynamic characteristics model 16 is restricted by thereference manipulated variable determiner 14 as previously described,thus preventing the occurrence of a spin or an extreme side slip of themodel vehicle.

[About the FB Distribution Law]

The details of the processing by the FB distribution law 20 will now beexplained with reference to FIG. 9 to FIG. 16.

FIG. 9 is a functional block diagram showing the processing function ofthe FB distribution law 20. As shown in the figure, the processingfunction of the FB distribution law 20 is roughly constituted of avirtual external force determiner 20 a which carried out the processingfor determining the virtual external forces Mvir and Fvir and anactuator operation FB target value determiner 20 b which carries out theprocessing for determining an actuator operation FB target value.

Incidentally, the virtual external force determiner 20 a corresponds tothe model state amount error response control means in the presentinvention, while the actuator operation FB target value determiner 20 bcorresponds to the actual vehicle state amount error response controlmeans in the present invention.

First, the virtual external force determiner 20 a will be explained withreference to FIG. 9. The processing function of the virtual externalforce determiner 20 a is roughly divided into a virtual external forcetemporary value determiner 201 and a γβ limiter 202.

In the processing by the virtual external force determiner 20 a, first,temporary values Mvirtmp and Fvirtmp of virtual external forces aredetermined by the virtual external force temporary value determiner 201on the basis of state amount errors γerr(=γact−γd), βerr(=βact−βd) inputfrom the subtracter 18. Mvirtmp of the temporary values Mvirtmp andFvirtmp means a moment (a moment in the yaw direction) to beadditionally generated about the center-of-gravity point Gd of the modelvehicle of the reference dynamic characteristics model 16 in order toapproximate the state amount errors γerr and βerr to zero, and Fvirtmpmeans a translational force (a lateral translational force of the modelvehicle) to be additionally applied to the center-of-gravity point Gd ofthe model vehicle of the reference dynamic characteristics model 16 inorder to approximate the state amount errors γerr and βerr to zero.

To be specific, as shown by expression 15 given below, a vector (γerr,βerr)^(T) (the superscript T means transposition) composed of the inputstate amount errors γerr and βerr is multiplied by a predetermined gainmatrix Kfvir thereby to determine the temporary values Mvirtmp andFvirtmp of the virtual external force (hereinafter referred to as thevirtual external force temporary values Mvirtmp and Fvirtmp).

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu} \;}{expression}{\mspace{11mu} \;}5} \rbrack & \; \\{{\begin{bmatrix}{Fvirtmp} \\{Mvirmp}\end{bmatrix} = {{Kfvir} \cdot \begin{bmatrix}{\beta \; {err}} \\{\gamma \; {err}}\end{bmatrix}}}{where}{{Kfvir} \equiv \begin{bmatrix}{{Kfvir}\; 11} & {{Kfvir}\; 12} \\{{Kfvir}\; 21} & {{Kfvir}\; 22}\end{bmatrix}}} & {{Expression}\mspace{14mu} 15}\end{matrix}$

According to the expression 15, the virtual external force temporaryvalues Mvirtmp and Fvirtmp as the temporary values of control inputs tobe fed back to the reference dynamic characteristics model 16 toapproximate the state amount errors γerr and βerr to zero are determinedfrom the state amount errors γerr and βerr by the feedback control law.

If it is required that the γβ limiter 202, which will be explained indetail below, generates an intense action for bringing βd or βact backto a predetermined permissible range only if the vehiclecenter-of-gravity point side slip angle βd of the model vehicle or theactual vehicle center-of-gravity point side slip angle βact of theactual vehicle 1 is about to exceed or has exceeded the permissiblerange, then βerr is desirably converged to zero by a characteristicclose to a primary delay characteristic with a small time constant. Forthis purpose, for example, Kfvir12 among gain matrix Kfvir componentsmay be set to zero and Kfvir11 may be set such that the absolute valuethereof increases.

Subsequently, the γβ limiter 202 carries out the processing forcorrecting the virtual external force temporary values Mvirtmp andFvirtmp so as to restrain the yaw rate γd and the vehiclecenter-of-gravity point side slip angle βd of the model vehicle on thereference dynamic characteristics model 16 from deviating from therespective predetermined permissible ranges thereof.

More specifically, the γβ limiter 202 first carries out the processingby a prediction calculator 203 to predict the yaw rate γd and thevehicle center-of-gravity point side slip angle βd of the model vehicleafter predetermined time (after the time equivalent to a predeterminednumber of one or more control processing cycles), and outputs thosepredicted values as the predicted yaw rate γda and a predicted vehiclecenter-of-gravity point side slip angle βda.

At this time, the prediction calculator 203 receives the reference yawrate γd (current time value) and the reference vehicle center-of-gravitypoint side slip angle βd (current time value) determined by thereference dynamic characteristics model 16, the actual travelingvelocity Vact (current time value) detected or estimated by thesensor/estimator 12, the second limited front wheel steering angleδf_ltd2 (current time value) determined by the reference manipulatedvariable determiner 14, and the virtual external force temporary valuesMvirtmp and Fvirtmp (current time values) determined as described aboveby the virtual external force temporary value determiner 201. Then, theprediction calculator 203 calculates the predicted yaw rate γda and thepredicted vehicle center-of-gravity point side slip angle βda on thebasis of the expression 01 on the assumption that the model front wheelsteering angle δf_d is held at the input δf_ltd2, the virtual externalforces Mvir and Fvir to be applied to the model vehicle are held at theinput Mvirtmp and Fvirtmp, and the traveling velocity Vd of the modelvehicle is held at the input Vact.

In the present embodiment, the predicted yaw rate γda and the predictedvehicle center-of-gravity point side slip angle βda correspond to therestriction object amounts in the present invention. In this case, theyaw rate γd and the vehicle center-of-gravity point side slip angle βdof the model vehicle are used as the second state amounts in the presentinvention.

Subsequently, the γβ limiter 202 passes the γda and βda calculated bythe prediction calculator 203 as described above through a γ dead-zoneprocessor 204 and a β dead-zone processor 205, respectively, todetermine the amounts of deviation γover and βover from predeterminedpermissible ranges of γda and βda, respectively. The graph of the γdead-zone processor 204 shown in the figure is a graph illustrating therelationship between γda and γover, the values in the direction of theaxis of abscissas related to the graph indicating the values of γda,while the values in the direction of the axis of ordinates indicatingthe values of γover. Similarly, the graph of the β dead-zone processor205 shown in the figure is a graph illustrating the relationship betweenβda and βover, the values in the direction of the axis of abscissasrelated to the graph indicating the values of βda, while the values inthe direction of the axis of ordinates indicating the values of βover.

The permissible range in the γ dead-zone processor 204 is a permissiblerange (a permissible range of the yaw rate γd) having the lower limitvalue and the upper limit value thereof set to γdamin(<0) andγdamax(>0), respectively, and the permissible range in the β dead-zoneprocessor 205 is a permissible range (a permissible range of the vehiclecenter-of-gravity point side slip angle βd) having the lower limit valueand the upper limit value thereof set to βdamin(<0) and βdamax(>0),respectively.

In the present embodiment, the permissible range [γdamin, γdamax]related to the yaw rate γd is set such that, for example, thecentrifugal force generated in the model vehicle when a normal circularturn is made while holding the traveling velocity Vd of the modelvehicle at Vact (current time value) and also holding the yaw rate γd ofthe model vehicle at γdamin or γdamax does not exceed a limit value of africtional force based on the estimated friction coefficient μestm(current time value). In other words, γdamax and γdamin are set on thebasis of Vact (current time value) and μestm (current time value) suchthat expressions 16a and 16b shown below are satisfied.

m·Vact·γdamax<μestm·m·g   Expression 16a

m·Vact·γdamin>−μestm·m·g   Expression 16b

γdamax, γdamin may be set such that, for example, the absolute value ofeach thereof will be the same value as the maximum yaw rate γmax at anormal circular turn determined according to the expression 05 (providedγdamax=γmax and γdamin=−γmax). Alternatively, however, the γdamax andγdamin may be set such that the absolute values thereof are differentvalues from γmax (e.g., values that are smaller than γmax).

Incidentally, the permissible range [γdamin, γdamax] set as describedabove narrows as the actual traveling velocity Vact increases or theestimated friction coefficient μestm decreases.

Further, the permissible range [βdamin, βdamax] related to the vehiclecenter-of-gravity point side slip angle βd is set, for example, within arange of a vehicle center-of-gravity point side slip angle thatmaintains the relationship between the vehicle center-of-gravity pointside slip angle of the actual vehicle 1 and the translational force inthe lateral direction applied to the center-of-gravity point of theactual vehicle 1 to be a substantially linear relationship (proportionalrelationship). In this case, βdamin and βdamax are desirably set on thebasis of at least one of Vact (current time value) and μestm (currenttime value).

Further, specifically, the processing by the γ dead-zone processor 204sets γover=0 if an input γda is a value within a predeterminedpermissible range [γdamin, γdamax] (if γdamin≦γda≦γdamax), or setsγover=γda−γdamin if γda<γdamin, or sets γover=γda−γdamax if γda>γdamax.Thus, the amount of deviation γover of the predicted yaw rate γda fromthe permissible range [γdamin, γdamax] is determined.

Similarly, the processing by the β dead-zone processor 205 sets βover=0if the value of an input βda is a value within a predeterminedpermissible range [βdamin, βdamax] (if βdamin≦βda≦βdamax), or setsβover=βda−βdamin if βda<βdamin, or sets βover=βda−βdamax if βda>βdamax.Thus, the amount of deviation βover of the predicted vehiclecenter-of-gravity point side slip angle βda from the permissible range[βdamin, βdamax] is determined.

Subsequently, the γβ limiter 202 calculates, by a processor 206, thetemporary value manipulated variables Mvir_over and Fvir_over, which arethe correction amounts of the virtual external force temporary valuesMvirtmp and Fvirtmp, such that these amounts of deviation γover andβover are approximated to zero.

To be more specific, as indicated by expression 17 given below, a vector(γover, βover)^(T) composed of γover and βover is multiplied by apredetermined gain matrix Kfov to determine Mvir_over and Fvir_over.

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu} \;}{expression}{\mspace{11mu} \;}6} \rbrack & \; \\{{\begin{bmatrix}{F\; {vir\_ over}} \\{M\; {vir\_ over}}\end{bmatrix} = {{Kfov} \cdot \begin{bmatrix}{\beta \mspace{11mu} {over}} \\{\gamma \mspace{11mu} {over}}\end{bmatrix}}}{where}{{Kfov} \equiv \begin{bmatrix}{{Kfov}\; 11} & {{Kfov}\; 12} \\{{Kfov}\; 21} & {{Kfov}\; 22}\end{bmatrix}}} & {{Expression}\mspace{14mu} 17}\end{matrix}$

Subsequently, the γβ limiter 202 subtracts the temporary valuemanipulated variables Mvir_over and Fvir_over from the virtual externalforce temporary values Mvirtmp and Fvirtmp by a subtracter 207 todetermine the current time values of the virtual external forces Mvirand Fvir. In other words, the virtual external forces Mvir and Fvir aredetermined according to the following expressions 18a and 18b.

Mvir=Mvirtmp−Mvir_over   Expression 18a

Fvir=Fvirtmp−Fvir_over   Expression 18b

The processing by the virtual external force determiner 20 a is carriedout as described above thereby to determine the virtual external forcesMvir and Fvir such that the state amount errors γerr and βerr areapproximated to zero, while restraining the predicted yaw rate γda andthe predicted vehicle center-of-gravity point side slip angle βda fromdeviating from the permissible ranges [γdamin, γdamax] and [βdamin,βdamax], respectively.

The γβ limiter 202 of the virtual external force determiner 20 aexplained above determines the virtual external forces Mvir and Fvir bycorrecting the virtual external force temporary values Mvirtmp andFvirtmp on the basis of the temporary value manipulated variablesMvir_over and Fvir_over (more generally speaking, Mvir and Fvir aredetermined by the linear coupling of Mvir_over and Mvirtmp and thelinear coupling of Fvir_over and Fvirtmp, respectively). Alternatively,however, the virtual external forces Mvir and Fvir may be determined asdescribed below. FIG. 10 is a functional block diagram for explainingthe processing.

Referring to the figure, in this example, the processing by the virtualexternal force temporary value determiner 201, the prediction calculator203, the γ dead-zone processor 204, the β dead-zone processor 205, and aprocessor 206 is the same as that shown in FIG. 9. Meanwhile, in thepresent example, the temporary value manipulated variables Fvir_over andMvir_over determined by the processor 206 are input to processors 208and 209, respectively, and correction coefficients Katt1(≧0) andKatt2(≧0) for correcting the virtual external force temporary valuesMvirtmp and Fvirtmp, respectively, are determined in the processors 208and 209. These correction coefficients Katt1 and Katt2 are correctioncoefficients serving as multipliers for the virtual external forcetemporary values Mvirtmp and Fvirtmp, respectively. The graph related tothe processor 208 shown in the figure is a graph illustrating therelationship between Mvir_over and Katt1, the values in the direction ofthe axis of abscissas related to the graph indicating the values ofMvir_over and the values in the direction of the axis of ordinatesindicating the values of Katt1. Similarly, the graph related to theprocessor 209 shown in the figure is a graph illustrating therelationship between Fvir_over and Katt2, the values in the direction ofthe axis of abscissas related to the graph indicating the values ofFvir_over and the values in the direction of the axis of ordinatesindicating the values of Katt2.

The processing by the processor 208 sets Katt1=1 if Mvir_over is zeroand sets the value of Katt1 such that the value of Katt1 monotonouslydecreases from 1 to 0 as the absolute value of Mvir_over increases fromzero, as shown by the graph in the figure. Further, the value of Katt1is maintained at zero if the absolute value of Mvir_over exceeds apredetermined value (a value at which Katt1 reaches zero).

Similarly, the processing by the processor 209 sets Katt2=1 if Fvir_overis zero and sets the value of Katt2 such that the value of Katt2monotonously decreases from 1 to 0 as the absolute value of Fvir_overincreases from zero, as shown by the graph in the figure. Further, thevalue of Katt2 is maintained at zero if the absolute value of Fvir_overexceeds a predetermined value (a value at which Katt2 reaches zero).

Subsequently, the correction coefficients Katt1 and Katt2 determined asdescribed above are multiplied by the virtual external force temporaryvalues Mvirtmp and Fvirtmp by multipliers 210 and 211, respectively,thereby determining the current time values of the virtual externalforces Mvir and Fvir.

Thus, in the example shown in FIG. 10, the virtual external force Mviris determined such that the magnitude of the virtual external force Mviris narrowed (approximated to zero) relative to the virtual externalforce temporary value Mvirtmp as the absolute value of the amount ofdeviation Mvir_over increases. Similarly, the virtual external forceFvir is determined such that the magnitude of the virtual external forceMvir is narrowed (approximated to zero) relative to the virtual externalforce temporary value Mvirtmp as the absolute value of the amount ofdeviation Fvir_over increases. Thus, determining the virtual externalforces Mvir and Fvir means to regard that the deviation of γda and βdafrom their permissible ranges is attributable to the virtual externalforces Mvir and Fvir and to determine the virtual external forces Mvirand Fvir such that the state amount errors γerr and βerr areapproximated to zero while restraining the deviation of γda and βda fromtheir permissible ranges [γdamin, γdamax] and [βdamin, βdamax]. In thiscase, desirably, in the reference manipulated variable determiner 14,the model front wheel steering angle δf_d to be input to the referencedynamic characteristics model 16 is limited, as described above.

Further, in the γβ limiter 202 explained above, the predicted yaw rateγda and the predicted vehicle center-of-gravity point side slip angleβda determined using expression 01 as described above by the predictioncalculator 203 are respectively defined as restriction object amounts,and these γda and βda are input to the γ dead-zone processor 204 and theβ dead-zone processor 205 to determine the deviation amounts γover andβover. Alternatively, however, in place of γda and βda, the current timevalues of the reference yaw rate γd and the reference vehiclecenter-of-gravity point side slip angle βd, or the current time valuesof the actual yaw rate γact and the actual vehicle center-of-gravitypoint side slip angle βact, or the values obtained by filtering thesevalues may be used as the restriction object amounts.

For example, at each control processing cycle, the current time value ofγd in place of γda may be input to the γ dead-zone processor 204, and avalue obtained by filtering, in which a transfer function is representedin the form of (1+T1·s)/(1+T2·s), the βd sequentially calculated by thereference dynamic characteristics model 16 (T1 and T2 denoting certaintime constants and s denoting a Laplace operator) may be input in placeof βda into the β dead-zone processor 205. In this case, if the timeconstants T1 and T2 are set such that, for example, T1>T2, then thefiltering functions as a so-called phase advancing compensation element.At this time, advancing the phase of a frequency component of βd in afrequency band which is high to a certain degree and enhancing a gainrelative to the frequency component make it possible to limit thevirtual external forces Mvir and Fvir on the basis of βover before thevalue itself of βd determined at each control processing cycle deviatesfrom the permissible range [βdamin, βdamax].

Further, the γda and βda as the restriction object amounts mayalternatively be determined as described below. In the predictioncalculator 203, as shown by the following expressions 19a and 19b, anappropriate coefficient cij may be used to determine, as γda and βda,the values obtained by linearly coupling the current time values of γdand βd.

γda=c11·γd+c12·βd   Expression 19a

βda=c21·γd+c22·βd   Expression 19b

Alternatively, as shown by the following expressions 20a and 20b, anappropriate coefficient cij may be used to determine, as γda and βda,the values obtained by linearly coupling the current time values of γd,βd, Mvirtmp, Fvirtmp, and δf_ltd2.

$\begin{matrix}{{\gamma \; {da}} = {{c\; {11 \cdot \gamma}\; d} + {c\; {12 \cdot \beta}\; d} + {c\; {13 \cdot {Mvirtmp}}} + {c\; {14 \cdot {Fvirtmp}}} + {c\; {15 \cdot \delta}\; {f\_}1{td}\; 2}}} & {20a} \\{{\beta \; {da}} = {{c\; {21 \cdot \gamma}\; d} + {c\; {22 \cdot \beta}\; d} + {c\; {23 \cdot {Mvirtmp}}} + {c\; {24 \cdot {Fvirtmp}}} + {c\; {25 \cdot \delta}\; {f\_}1{td}\; 2}}} & {20b}\end{matrix}$

These expressions 20a and 20b are represented by further generalizingthe processing by the prediction calculator 203 described above.

Alternatively, as shown by the following expressions 21a and 21b, anappropriate coefficient cij may be used to determine, as γda and βda,the values obtained by linearly coupling the current time values of γactand βact. Incidentally, in this case, γact and βact will be used as thesecond state amounts in the present invention.

γda=c11·γact+c12·βact   Expression 21a

βda=c21·γact+c22·βact   Expression 21b

Supplementally, as is obvious from expression 02b, if c21=−Lr/Vd andc22=1 (here, Vd denotes the traveling velocity of the model vehicle(=actual traveling velocity Vact)), then βda corresponds to the sideslip angle of the rear wheel.

Alternatively, as shown in the following expressions 22a and 22b, anappropriate coefficient cij may be used to determine, as γda and βda,the values obtained by linearly coupling the current time values of γd,βd and a temporal differential value dβd/dt of βd, γact, βact and atemporal differential value dβact/dt of βact, Mvirtmp, Fvirtmp, andδf_ltd2. Incidentally, in this case, γd, βd, γact and βact will be usedas the second state amounts in the present invention.

$\begin{matrix}{{\gamma \; {da}} = {{c\; {11 \cdot \gamma}\; d} + {c\; {12 \cdot \beta}\; d} + {c\; {13 \cdot {\; \beta}}\; {d/{t}}} + {c\; {14 \cdot \gamma}\; {act}} + {c\; {15 \cdot \beta}\; {act}} + {c\; {16 \cdot {\; \beta}}\; {{act}/{t}}} + {c\; {17 \cdot {Mvirtmp}}} + {c\; {18 \cdot {Fvirtmp}}} + {c\; {19 \cdot \delta}\; {f\_}1{td}\; 2}}} & {22a} \\{{\gamma \; {da}} = {{c\; {21 \cdot \gamma}\; d} + {c\; {22 \cdot \beta}\; d} + {c\; {23 \cdot {\; \beta}}\; {d/{t}}} + {c\; {24 \cdot \gamma}\; {act}} + {c\; {25 \cdot \beta}\; {act}} + {c\; {26 \cdot {\; \beta}}\; {{act}/{t}}} + {c\; {27 \cdot {Mvirtmp}}} + {c\; {28 \cdot {Fvirtmp}}} + {c\; {29 \cdot \delta}\; {f\_}1{td}\; 2}}} & {22b}\end{matrix}$

Alternatively, the weighted mean value of the value of the computationresult of the right side of expression 20a and the value of thecomputation result of the right side of expression 21a and the weightedmean value of the value of the computation result of the right side ofexpression 20b and the value of the computation result of the right sideof expression 21b may be determined as γda and βda, respectively. Thisis an example of the case where γda and βda are determined according toexpression 22a and expression 22b. The terms of Mvirtmp and Fvirtmp inexpression 20a and expression 20b or expression 22a and expression 22bmay be omitted.

Alternatively, the predicted values of γd and βd at each controlprocessing cycle until after predetermined time may be determinedaccording to the expression 01 and the peak values of the determined γdand βd may be determined as γda and βda.

Further, even in the case where γda and βda are determined using any ofexpression 20a and expression 20b, or expression 21a and expression 21b,or expression 22a and expression 22b, the coefficient cij of theseexpressions may be provided with a frequency characteristic (in otherwords, the value of a variable to be multiplied by cij may be subjectedto filtering by a low-pass filter or the like). Alternatively, thelimitation of a temporal change rate of the variable may be placed onthe value of the variable to be multiplied by the coefficient cij.

Supplementally, if γda and βda are determined by expression 21a andexpression 21b or expression 22a and expression 22b described above,then each coefficient cij is desirably set such that the γda and βdabear meanings as the predicted values of the actual yaw rate γact andthe actual vehicle center-of-gravity point side slip angle βact of theactual vehicle 1 after predetermined time.

If the reference dynamic characteristics model 16 is a linear model asrepresented by the expression 01, then γda and βda can be properlydetermined as the predicted values of a yaw rate and a vehiclecenter-of-gravity point side slip angle of the actual vehicle 1 or themodel vehicle after predetermined time by using any of expression 20aand expression 20b, or expression 21a and expression 21b, or expression22a and expression 22b.

If the current time values of γact and βact or the values obtained byfiltering γact and βact are used in place of γda and βda, or if γda andβda are determined by expression 21a and expression 21b or expression22a and expression 22b described above, then the virtual external forcesMvir and Fvir will be determined such that the state amount errors γerrand βerr are approximated to zero while restraining the current timevalues or filtered values or predicted values of the actual yaw rateγact and the actual vehicle center-of-gravity point side slip angle βactof the actual vehicle 1 from deviating from the permissible ranges[γdamin, γdamax] and [βdamin, βdamax], respectively.

Supplementally, more generally, the processing by the virtual externalforce determiner 20 a may determine the virtual external forces Mvir andFvir according to expression 200 given below.

$\begin{matrix}\lbrack {{Mathematical}\mspace{14mu} {expression}\mspace{14mu} 7} \rbrack & \; \\{\begin{bmatrix}{F\; {vir}} \\{M\; {vir}}\end{bmatrix} = {\quad{\begin{bmatrix}{{Kfb}\; 11} & {{Kfb}\; 12} & {{Kfb}\; 13} & {{Kfb}\; 14} & {{Kfb}\; 15} & {{{Kfb}\; 16}\;} \\{{Kfb}\; 21} & {{Kfb}\; 22} & {{Kfb}\; 23} & {{Kfb}\; 24} & {{Kfb}\; 25} & {{Kfb}\; 26}\end{bmatrix} \cdot {\quad{\begin{bmatrix}{\beta \; d} \\{\gamma \; d} \\{\beta \; {act}} \\{\gamma \; {act}} \\{\beta \mspace{11mu} {over}} \\{\gamma \mspace{11mu} {over}}\end{bmatrix} + {{\begin{bmatrix}{K\; {fb\_\delta}\; 1} \\{K\; {fb\_\delta}\; 2}\end{bmatrix} \cdot \delta}\; {f\_ ltd}\; 2}}}}}} & {{Expression}{\mspace{11mu} \;}200}\end{matrix}$

Further, in the γ dead-zone processor 204 and the β dead-zone processor205 of the γβ limiter 202, the amounts of deviation γover and βover havebeen determined by separately setting the permissible ranges [γdamin,γdamax] and [βdamin, βdamax] of γda and βda, respectively;alternatively, however, a permissible range (permissible area) for apair of γda and βda may be set by considering the correlativity betweenγda and βda, to determine the amounts of deviation γover and βover.

For example, as shown in FIG. 11, an area A (a parallelogram area)enclosed by straight lines 1 to 4 on a coordinate plane having γda onthe axis of abscissa and βda on the axis of ordinates is set as apermissible area A for a pair of γda and βda. In this case, the straightlines 1 and 3 are the straight lines that define a lower limit value andan upper limit value, respectively, of γda. The lower limit value andthe upper limit value are set, for example, in the same manner as thatfor the lower limit value γdamin and the upper limit value γdamax of thepermissible range [γdamin, γdamax] in the γ dead-zone processor 204. Thestraight lines 2 and 4 are the straight lines that define a lower limitvalue and an upper limit value, respectively, of βda. In this example,the setting is made such that the lower limit value and the upper limitvalue, respectively, linearly change according to γda. Further, theamounts of deviation γover and βover are determined, for example, asfollows. Namely, if the pair of γda and βda exists within thepermissible area A, as indicated by a point P1 in FIG. 11, thenγover=βover=0. On the other hand, if the pair of γda and βda deviatesfrom the permissible area A, as indicated by, for example, a point P2 inFIG. 11, then a point P3 on the boundary of the permissible area A thatis closest to the point P2 among the points on the straight line 5 whichpasses the point P2 and has a predetermined inclination (a point P3closest to P2 among the points existing in the permissible area A on astraight line 5) is determined. Then, the difference between the valueof γda at the point P2 and the value of γda at the point P3 isdetermined as the amount of deviation γover, and the difference betweenthe value of βda at the point P2 and the value of βda at the point P3 isdetermined as the amount of deviation βover. If a point associated withthe pair of γda and βda is, for example, a point P4 shown in FIG. 11,i.e., if a straight line 6 having a predetermined inclination (the sameinclination as that of the straight line 5) to pass the point P4associated with the pair of γda and βda does not intersect with thepermissible area A (if no point exists in the permissible range A on thestraight line 6), then a point P5 on the boundary of the permissiblearea A that is closest to the straight line 6 is determined. Then, thedifference between the value of γda at the point P4 and the value of γdaat the point P5 may be determined as the amount of deviation γover, andthe difference between the value of βda at the point P4 and the value ofβda at the point P5 may be determined as the amount of deviation βover.

Supplementally, the permissible area of the pair of γda and βda does nothave to be a parallelogram area, and it may alternatively be, forexample, an area A′ having smooth boundary portions (formed with noangular portions), as indicated by the dashed line in FIG. 11.

Further, in the γβ limiter 202, the amounts of deviation γover and βoverfrom [γdamin, γdamax] and [βdamin, βdamax] have been determined on bothγda and βda, then the temporary values Mvirtmp and Fvirtmp have beencorrected on the basis thereof; alternatively, however, the temporaryvalues Mvirtmp and Fvirtmp may be corrected on the basis of only one ofγover and βover. In this case, the processing by the processor 206 maydetermine the temporary value manipulated variables Mvir_over andFvir_over by fixing the value of either one of γover and βover to zero.

Next, the processing by the actuator operation FB target valuedeterminer 20 b will be explained with reference to FIG. 12 to FIG. 14.In the following explanation, the wheels W1 to W4 may be referred to asan n-th wheel Wn (n=1, 2, 3, 4).

FIG. 12 is a functional block diagram showing the processing by theactuator operation FB target value determiner 20 b. Referring to thefigure, the actuator operation FB target value determiner 20 b firstdetermines in a processor 220 a feedback yaw moment basic required valueMfbdmd, which is a basic required value of a moment in the yaw directionto be generated about the center-of-gravity point G of the actualvehicle 1 in order to bring the state amount errors γerr and βerr closeto zero on the basis of received state amount errors γerr and βerr, asthe basic required value of a feedback control input to the actuatordevice 3 of the actual vehicle 1.

Mfbdmd is a feedback required amount determined according to a feedbackcontrol law from the state amount errors γerr and βerr. Morespecifically, as indicated by expression 23 given below, a vector (βerr,γerr)^(T) composed of βerr and γerr is multiplied by a predeterminedgain matrix Kfbdmd (by linearly coupling βerr and γerr), therebydetermining Mfbdmd.

$\begin{matrix}\lbrack {{Mathematical}{\mspace{11mu} \;}{expression}{\mspace{11mu} \;}8} \rbrack & \; \\{{{Mfbdmd} = {{Kfbdmd} \cdot \begin{bmatrix}{\beta \; {err}} \\{\gamma \; {err}}\end{bmatrix}}}{where}{{Kfbdmd} \equiv \begin{bmatrix}{{Kfbdmd}\; 1} & {{Kfbdmd}\; 2}\end{bmatrix}}} & {{Expression}\mspace{14mu} 23}\end{matrix}$

Alternatively, Mfbdmd may be determined on the basis of βerr, γerr and afirst-order differential value dβerr/dt of βerr. For example, a vectorcomposed of βerr, γerr and dβerr/dt may be multiplied by an appropriategain matrix (by linearly coupling βerr, γerr, and dβerr/dt by anappropriate coefficient) so as to determine Mfbdmd.

Alternatively, at least one of elements Kfbdmd1 and Kfbdmd2 of the gainmatrix Kfbdmd may be multiplied by a phase compensating element whosetransfer function is expressed by (1+Tc1·s)/(1+Tc2·s). For instance,Kfbdmd1, which is a multiplier for βerr, may be multiplied by the phasecompensating element, and the values of time constants Tc1 and Tc2 maybe set such that Tc1>Tc2. In such a case, the term obtained bymultiplying Kfbdmd1 by βerr will be equivalent to the result obtained bypassing βerr and a differential value thereof, which have been linearlycoupled, through a high-cut filter.

Supplementally, the feedback yaw moment basic required value Mfbdmdcorresponds to the actual vehicle feedback required amount in thepresent invention.

Subsequently, the actuator operation FB target value determiner 20 bpasses the Mfbdmd through a dead-zone processor 221 to determine a deadzone excess feedback yaw moment required value Mfbdmd_a. The graph ofthe dead zone processor 221 in the figure is a graph illustrating therelationship between Mfbdmd and Mfbdmd_a, the values in the direction ofthe axis of abscissas related to the graph indicating the values ofMfbdmd, while the values in the direction of the axis of ordinatesindicating the values of Mfbdmd_a.

According to the present embodiment, in the feedback control of theactuator devices 3 of the actual vehicle 1, the braking device of thedriving/braking device 3A among the actuator devices 3 is mainlyoperated to approximate the state amount errors γerr and βerr to zero.In this case, if the braking device is operated on the basis of Mfbdmddetermined as described above, there is a danger that the braking devicewill be frequently operated. To prevent this, according to the presentembodiment, the braking device is operated on the basis of the dead zoneexcess feedback yaw moment required value Mfbdmd_a obtained by passingMfbdmd through the dead zone processor 221.

To be more specific, the processing by the dead zone processor 221 iscarried out as follows. The dead zone processor 221 sets Mfbdmd_a=0 ifthe value of Mfbdmd exists in a predetermined dead zone established inthe vicinity of zero. Further, the dead zone processor 221 setsMfbdmd_a=Mfbdmd−upper limit value if Mfbdmd is larger than an upperlimit value (>0) of the dead zone, while the dead zone processor 221sets Mfbdmd_a=Mfbdmd−lower limit value if Mfbdmd is smaller than a lowerlimit value (<0) of the dead zone. In other words, an excess (the amountof deviation) from the dead zone of Mfbdmd is determined as Mfbdmd_a.Operating the braking device of the driving/braking device 3A on thebasis of Mfbdmd_a determined as described above makes it possible tooperate the braking device such that the state amount errors γerr andβerr are approximated to zero, while restraining frequent operation ofthe braking device based on the state amount errors γerr and βerr.

Supplementally, in the present embodiment, the dead zone of thedead-zone processor 221 corresponds to the dead zone in the presentinvention. Further, a predetermined value in the dead zone is set tozero.

Subsequently, an actuator operation FB target value distributionprocessor 222 carries out processing for determining the actuatoroperation FB target value (a feedback control input to an actuatordevice 3) on the basis of the dead zone excess feedback yaw momentrequired value Mfbdmd_a.

The processing by the actuator operation FB target value distributionprocessor 222 will be schematically explained. The actuator operation FBtarget value distribution processor 222 determines an FB target n-thwheel brake driving/braking force Fxfbdmd_n (n=1, 2, 3, 4), which is afeedback target value of the driving/braking force of the wheels W1 toW4 by an operation of the braking device of the driving/braking device3A (a feedback control input to the braking device to approximate γerrand βerr to zero), such that Mfbdmd_a is generated about thecenter-of-gravity point of the actual vehicle 1 (consequently toapproximate γerr and βerr to zero). Alternatively, in addition toFxfbdmd_n (n=1, 2, 3, 4), an active steering FB target lateral forceFyfbdmd_f, which is a feedback target value of the lateral forces of thefront wheels W1 and W2 by an operation of the steering device 3B, isdetermined.

In this case, according to the present embodiment, if the dead zoneexcess feedback yaw moment required value Mfbdmd_a indicates a moment inthe positive direction (a moment in the counterclockwise direction asobserved from above the actual vehicle 1), then basically, thedriving/braking force of the left wheels W1 and W3 of the actual vehicle1 is increased in the braking direction thereby to determine the FBtarget n-th wheel brake driving/braking force Fxfbdmd_n (n=1, 2, 3, 4)such that Mfbdmd_a is generated about the center-of-gravity point G ofthe actual vehicle 1. Further, at this time, an FB target first wheelbrake driving/braking force Fxfbdmd_1 and an FB target third wheel brakedriving/braking force Fxfbdmd_3 related to the left wheels W1 and W3 forgenerating Mfbdmd_a about the center-of-gravity point G of the actualvehicle 1 are determined such that the relationship between the changesin each thereof and the changes in Mfbdmd_a is a proportionalrelationship. Hereinafter, the ratios of changes in Fxfbdmd_1 andFxfbdmd_3, respectively, to the changes in Mfbdmd_a in the proportionalrelationship will be referred to as a front wheel gain GA1 and a rearwheel gain GA3, respectively. In the present embodiment, if Mfbdmd_a isa moment in the positive direction, then Fxfbdmd_1 and Fxfbdmd_3 aredetermined to be the values obtained by multiplying Mfbdmd_a by GA1 andGA3, respectively, (values that are proportional to Mfbdmd_a).

If Mfbdmd_a is a moment in the negative direction (a moment in theclockwise direction as observed from above the actual vehicle 1), thenbasically, the driving/braking force of the right wheels W1 and W3 ofthe actual vehicle 1 is increased in the braking direction so as todetermine the FB target n-th wheel brake driving/braking force Fxfbdmd_n(n=1, 2, 3, 4) such that Mfbdmd_a is generated thereby about thecenter-of-gravity point G of the actual vehicle 1. Further, at thistime, an FB target second wheel brake driving/braking force Fxfbdmd_2and an FB target fourth wheel brake driving/braking force Fxfbdmd_4related to the right wheels W2 and W4 for generating Mfbdmd_a about thecenter-of-gravity point G of the actual vehicle 1 are determined suchthat the relationship between the changes of each thereof and thechanges in Mfbdmd_a is a proportional relationship. Hereinafter, theratios of changes in Fxfbdmd_2 and Fxfbdmd_4, respectively, to changesin Mfbdmd_a in the proportional relationship will be referred to as afront wheel gain GA2 and a rear wheel gain GA4. In the presentembodiment, if Mfbdmd_a is a moment in the negative direction, thenFxfbdmd_2 and Fxfbdmd_4 are determined to be the values obtained bymultiplying Mfbdmd_a by GA2 and GA4, respectively, (values that areproportional to Mfbdmd_a).

In the following explanation, as shown in FIG. 13, the interval betweenthe front wheels W1 and W2 (i.e., the tread of the front wheels W1 andW2) of the actual vehicle 1 is denoted by df, and the interval betweenthe rear wheels W3 and W4 (i.e., the tread of the rear wheels W3 and W4)is denoted by dr, and the actual steering angle of the front wheels W1and W2 (the actual front wheel steering angle) is denoted by δf_act. Thedistance between an n-th wheel Wn and the center-of-gravity point G ofthe actual vehicle 1 in the direction orthogonal to the longitudinaldirection of the n-th wheel Wn (in the direction orthogonal on ahorizontal plane) when the actual vehicle 1 is observed from above isdenoted by Ln (n=1, 2, 3, 4). In the present embodiment, although therear wheels W3 and W4 are not shown because they are non-steeringcontrol wheels, the actual steering angle of the rear wheels W3 and W4(actual rear wheel steering angle) is denoted by δr_act. In the presentembodiment, δr_act=0 and L3=L4=dr/2.

Lf in FIG. 13 denotes the distance in the longitudinal direction betweenthe center-of-gravity point G of the actual vehicle 1 and the axle ofthe front wheels W1 and W2, and Lr denotes the distance in thelongitudinal direction between the center-of-gravity point G of theactual vehicle 1 and the axle of the rear wheels W1 and W2. The valuesof these Lf and Lr are the same as the values of Lf and Lr related tothe model vehicle shown in FIG. 3 described above.

The processing by the actuator operation FB target value distributionprocessor 222 will be specifically explained below. First, it is assumedthat the actual vehicle 1 is in a traveling-straight state (a travelingstate in which δf_act=0), and an n-th wheel driving/braking force fullrequired value Fxfullfbdmd_n, which is the driving/braking force of then-th wheel Wn (n=1, 2, 3, 4) required to generate a moment in the yawdirection that is equal to Mfbdmd_a about the center-of-gravity point Gof the actual vehicle 1 in the traveling-straight state is respectivelydetermined by a processor 222 a _(—) n (n=1, 2, 3, 4).

To be more specific, Fxfullfbdmd_n (n=1, 2, 3, 4) is determined in eachprocessor 222 a _(—) n by the multiplication calculation of thefollowing expressions 24a to 24d.

Fxfullfbdmd _(—)1=−(2/df)·Mfbdmd _(—) a   Expression 24a

Fxfullfbdmd _(—)2=(2/df)·Mfbdmd _(—) a   Expression 24b

Fxfullfbdmd _(—)3=−(2/dr)·Mfbdmd _(—) a   Expression 24c

Fxfullfbdmd _(—)4=(2/dr)·Mfbdmd _(—) a   Expression 24d

Subsequently, the actuator operation FB target value distributionprocessor 222 determines a first wheel distribution ratio correctionvalue K1_str and a second wheel distribution ratio correction valueK2_str in processors 222 b_1 and 222 b_2, respectively, on the basis ofthe actual front wheel steering angle δf_act, and also determines athird wheel distribution ratio correction value K3_str and a fourthwheel distribution ratio correction value K4_str in processors 222 b_3and 222 b_4, respectively, on the basis of the actual rear wheelsteering angle δr_act. These respective n-th wheel distribution ratiocorrection values Kn_str(n=1, 2, 3, 4) are correction coefficientswhereby Fxfullfbdmd_n is multiplied.

As the actual front wheel steering angle δf_act changes from zero, thedriving/braking forces of the first wheel W1 and the second wheel W2that generate a moment in the yaw direction equivalent to Mfbdmd_a aboutthe center-of-gravity point G of the actual vehicle 1 change fromFxfullfbdmd_1 and Fxfullfbdmd_2 determined according to the aforesaidexpressions 24a and 24b, respectively. Similarly, if the rear wheels W3and W4 are steering control wheels, then as the actual rear wheelsteering angle δr_act changes from zero, the driving/braking forces ofthe third wheel W3 and the fourth wheel W4 that generate a moment in theyaw direction equivalent to Mfbdmd_a about the center-of-gravity point Gof the actual vehicle 1 change from Fxfullfbdmd_3 and Fxfullfbdmd_4determined according to the expressions 24c and 24d, respectively. Then-th wheel distribution ratio correction value Kn_str is basically acorrection coefficient for determining the driving/braking force of then-th wheel Wn that generates a moment in the yaw direction equal orclose to Mfbdmd_a about the center-of-gravity point G of the actualvehicle 1 by correcting Fxfullfbdmd_n (n=1, 2, 3, 4), taking suchinfluences of a steering angle into account.

In the present embodiment, however, the rear wheels W3 and W4 arenon-steering control wheels, so that δr_act is always zero. Hence,K3_str and K4_str are in fact always set to “1.” Therefore, theprocessors 222 b_3 and 222 b_4 may be omitted.

Meanwhile, K1_str and K2_str related to the front wheels W1 and W2 aredetermined as described below by the processors 222 b_1 and 222 b_2,respectively. First, the values of L1 and L2 shown in FIG. 13 arecalculated by the geometric calculation of expressions 25a and 25b shownbelow from values of df and Lf, which are set beforehand, and a value ofδf_act. As the value of δf_act in the calculation, a value (current timevalue) detected or estimated by the sensor/estimator 12 may be used, oralternatively, a last time value of a target value (a target valuefinally determined at each control processing cycle) of a steering angleof the front wheels W1 and W2 of the actual vehicle 1 may be used.Further, if the steering device 3B is a mechanical steering device, thenthe value may be determined from an overall steering ratio of themechanical steering device and the steering angle θh in the driveoperation inputs. Alternatively, a current time value of the unlimitedfront wheel steering angle δf_unltd determined by the processor 14 a ofthe reference manipulated variable determiner 14 may be used.

L1=(df/2)·cos δf_act−Lf·sin δf_act   Expression 25a

L2=(df/2)·cos δf_act+Lf·sin δf_act   Expression 25b

The result obtained by multiplying the driving/braking force of each ofthe front wheels W1 and W2 by L1 and L2, respectively, provides themoment in the yaw direction generated about the center-of-gravity pointG of the actual vehicle 1. Therefore, basically, the driving/brakingforces of the front wheels W1 and W2 for generating a moment in the yawdirection that is equal to Mfbdmd_a about the center-of-gravity point Gcan be determined by multiplying Fxfullfbdmd_1 and Fxfullfbdmd_2 byK1_str=(df/2)/L1 and K2_str=(df/2)/L2, respectively.

Doing as described above, however, tends to cause K1_str or K2_str tobecome excessive when L1 or L2 is small and to cause the overallfeedback loop gain of the actual vehicle 1 based on the state amounterrors γerr and βerr to become excessive, frequently resulting in anoscillation of a control system or the like.

In the present embodiment, therefore, K1_str and K2_str are determinedaccording to the following expressions 26a and 26b.

K1_(—) str=(df/2)/max(L1, Lmin)   Expression 26a

K2_(—) str=(df/2)/max(L2, Lmin)   Expression 26b

where, in expression 26a and expression 26b, max(a,b) (a and b denotegeneral variables) denotes a function outputting a value of the variablea or b, whichever is larger, and Lmin denotes a positive constant thatis smaller than df/2. This has prevented K1_str and K2_str from becomingexcessive. In other words, according to the present embodiment,(df/2)/Lmin(>1) is defined as the upper limit value of K1_str andK2_str, and K1_str and K2_str are set at the upper limit value or lesson the basis of the actual front wheel steering δf_act.

In the present embodiment, the rear wheels W3 and W4 are non-steeringcontrol wheels, so that K3_str=K4_str=1, as described above. If,however, the rear wheels W3 and W4 are steering control wheels, thenK3_str and K4_str are desirably set on the basis of the actual rearwheel steering angle δr_act in the same manner as that for settingK1_str and K2_str on the basis of the actual front wheel steering angleδf_act as described above.

Subsequently, the actuator operation FB target value distributionprocessor 222 determines the n-th wheel distribution gain Kn in theprocessor 222 c _(—) n (n=1, 2, 3, 4) on the basis of the actual frontwheel side slip angle βf_act (current time value) or the actual rearwheel side slip angle βr_act (current time value). This Kn is acorrection coefficient (a positive value that is smaller than 1) forcorrecting Fxfullfbdmd_n by multiplying the n-th wheel driving/brakingforce full required value Fxfullfbdmd_n by Kn.

In this case, the n-th wheel distribution gain Kn is determined asdescribed below in each processor 222 c _(—) n.

A first wheel distribution gain K1 and a third wheel distribution gainK3 related to the first wheel W1 and the third wheel W3, which arelongitudinally disposed on the left side of the actual vehicle 1, aredetermined such that the gains virtually continuously change on thebasis of βf_act and βr_act, as shown by the solid-line graphs in FIGS.14( a) and (b), respectively. Further, a second wheel distribution gainK2 and a fourth wheel distribution gain K4 related to the second wheelW2 and the fourth wheel W4, which are longitudinally disposed on theright side of the actual vehicle 1, are determined such that the gainsvirtually continuously change on the basis of βf_act and βr_act, asshown by the dashed-line graphs in FIGS. 14( a) and (b), respectively.Incidentally, any one value of Kn is a positive value that is smallerthan 1. Further, “virtually continuously” means that a jump(quantization) of a value that inevitably occurs when an analog quantityis expressed in terms of a discrete system does not impair thecontinuity of the analog quantity.

In this case, more specifically, regarding the first wheel distributiongain K1 and the third wheel distribution gain K3, K1 is determined onthe basis of a value of βf_act such that it monotonously increases froma predetermined lower limit value to a predetermined upper limit valueas βf_act increases from a negative value to a positive value, as shownby the solid-line graph in FIG. 14( a). Hence, K1 is determined suchthat, when βf_act takes a positive value, it takes a larger value thanthat when βf_act takes a negative value.

Meanwhile, K3 is determined on the basis of a value of βr_act such thatit monotonously decreases from a predetermined upper limit value to apredetermined lower limit value as βr_act increases from a negativevalue to a positive value, as shown by the solid-line graph in FIG. 14(b). Hence, K3 is determined such that, when βr_act takes a negativevalue, it takes a larger value than that when βr_act takes a positivevalue.

The solid-line graphs in FIGS. 14( a) and (b) are set such that the sumof the values of K1 and K3 corresponding to βf_act and βr_act becomessubstantially one when βf_act and βr_act agree or substantially agreewith each other.

Further, regarding the second wheel distribution gain K2 and the fourthwheel distribution gain K4, K2 is determined on the basis of a value ofβf_act such that it monotonously decreases from a predetermined upperlimit value to a predetermined lower limit value as βf_act increasesfrom a negative value to a positive value, as shown by the dashed-linegraph in FIG. 14( a). In this case, the dashed-line graph indicating arelationship between K2 and βf_act is identical to the graph obtained bylaterally reversing the solid-line graph indicating a relationshipbetween K1 and βf_act around the axis of ordinates (the line ofβf_act=0). Hence, the value of K2 at each value of βf_act is determinedsuch that it is equal to the value of K1 at the value obtained byreversing the positive/negative of βf_act.

Further, K4 is determined on the basis of a value of βr_act such that itmonotonously increases from a predetermined lower limit value to apredetermined upper limit value as βr_act increases from a negativevalue to a positive value, as shown by the dashed-line graph in FIG. 14(b). In this case, the dashed-line graph indicating the relationshipbetween K4 and βr_act is identical to a graph obtained by laterallyreversing the solid-line graph indicating the relationship between K3and βr_act around the axis of ordinates (the line of βr_act=0). Hence,the value of K4 at each value of βr_act is determined such that it isequal to the value of K3 at the value obtained by reversing thepositive/negative of βr_act.

By determining the n-th wheel distribution gain Kn(n=1, 2, 3, 4) asdescribed above, in a situation wherein βf_act and βr_act take virtuallythe same value, such as when the actual vehicle 1 is in a normaltraveling mode, the ratio of the first wheel distribution gain K1corresponding to the front wheel W1 to the third wheel distribution gainK2 corresponding to the rear wheel W3 right behind the front wheel W1will monotonously change as βf_act and βr_act change while maintainingthe sum of K1 and K3 to be substantially constant. Similarly, the ratioof the second wheel distribution gain K2 corresponding to the frontwheel W2 to the fourth wheel distribution gain K4 corresponding to therear wheel W4 right behind the front wheel W2 will monotonously changeas βf_act and βr_act change while maintaining the sum of K2 and K4 to besubstantially constant.

The reason for determining the n-th wheel distribution gain Kn(n=1, 2,3, 4) on the basis of βf_act and βr_act as described above will bediscussed later.

Supplementally, in the present embodiment, βf_act and βr_act are used asa front wheel gain adjustment parameter and a rear wheel adjustmentparameter, and on the basis thereon, the n-th wheel distribution gain Knis changed as described above. Thus, as will be described later, thefront wheel gains GA1 and GA2 are changed on the basis of βf_act as thefront wheel gain adjustment parameter, and the rear wheel gains GA3 andGA4 are changed on the basis of βr_act as the rear wheel gain adjustmentparameter. In this case, βf_act has a meaning as a state amount relatedto lateral motions of the front wheels W1 and W2, and βr_act has ameaning as a state amount related to lateral motions of the rear wheelsW3 and W4. To determine the n-th wheel distribution gain Kn(n=1, 2)related to the front wheels W1 and W2, respectively, βf_act detected orestimated for each of the front wheels W1 and W2 may be used;alternatively, however, βf_act detected or estimated on either one ofthe front wheels W1 or W2, or a mean value of βf_act detected orestimated for each of the front wheels W1 and W2 may be defined as arepresentative value of actual front wheel side slip angles, and boththe distribution gains K1 and K2 may be determined on the basis of therepresentative value. This applies also when determining thedistribution gains K3 and k4 related to the rear wheels W3 and W4.

After determining Kn_str and Kn(n=1, 2, 3, 4) as described above, theactuator operation FB target value distribution processor 222 multiplieseach n-th wheel driving/braking force full required value Fxfullfbdmd_n(n=1, 2, 3, 4) by Kn_str and Kn by the processors 222 b _(—) n and 222 c_(—) n, respectively, thereby determining the n-th wheel distributiondriving/braking force basic value Fxfb_n. In other words, the n-th wheeldistribution driving/braking force basic values Fxfb_n (n=1, 2, 3, 4)are determined according to the following expressions 27a to 27d.

Fxfb _(—)1=Fxfullfbdmd _(—)1·K1_(—) str·K1   Expression 27a

Fxfb_(—)2=Fxfullfbdmd_(—)2·K2_str·K2   Expression 27b

Fxfb_(—)3=Fxfullfbdmd_(—)3·K3_str·K3   Expression 27c

Fxfb_(—)4=Fxfullfbdmd_(—)4·K4_str·K4   Expression 27d

When Fxfb_n(n=1, 2, 3, 4) is determined as described above, ifMfbdmd_a>0, then Fxfb_1 and Fxfb_3 associated with the left wheels W1and W3 provide a driving/braking force in a braking direction (anegative driving/braking force), while Fxfb_2 and Fxfb_4 associated withthe right wheels W2 and W4 provide a driving/braking force in a drivingdirection (a positive driving/braking force). Further, if Mfbdmd_a<0,then Fxfb_1 and Fxfb_3 associated with the left wheels W1 and W3 providea driving/braking force in the driving direction (a positivedriving/braking force), while Fxfb_2 and Fxfb_4 associated with theright wheels W2 and W4 provide a driving/braking force in the brakingdirection (a negative driving/braking force). Further, any one of then-th wheel distribution driving/braking force basic value Fxfb_n will beproportional to Mfbdmd_a.

Subsequently, the actuator operation FB target value distributionprocessor 222 passes the n-th wheel distribution driving/braking forcebasic value Fxfb_n(n=1, 2, 3, 4), which has been determined as describedabove, through a limiter 222 d _(—) n associated with each n-th wheel Wnthereby to determine respective FB target n-th wheel brakedriving/braking force Fxfbdmd_n, which is the feedback target value ofthe driving/braking force of the n-th wheel Wn by an operation of thebraking device of the driving/braking device 3A.

The graphs of the limiters 222 d _(—) n(n=1, 2, 3, 4) in FIG. 12 aregraphs showing the relationships between Fxfb_n and Fxfbdmd_n, thevalues in the direction of the axis of abscissas related to the graphsindicating the values of Fxfb_n, while the values in the direction ofthe axis of ordinates indicating the values of Fxfbdmd_n.

The limiter 222 d _(—) n outputs Fxfb_n directly as Fxfbdmd_n withoutprocessing it only if the value of Fxfb_n input thereto is zero or anegative value, and if Fxfb_n takes a positive value, then the value ofFxfbdmd_n to be output independently of a value of Fxfb_n is set tozero. In other words, Fxfbdmd_n is determined by limiting Fxfb_n withzero being an upper limit value.

The FB target n-th wheel brake driving/braking force Fxfbdmd_n isrespectively determined as described above so as to increase thedriving/braking forces of the left wheels W1 and W3 of the actualvehicle 1 in the braking direction (to set Fxfbdmd_1<0 and Fxfbdmd_3<0)if Mfbdmd_a>0, as described above, thereby to determine the FB targetn-th wheel brake driving/braking force Fxfbdmd_n(n=1, 2, 3, 4) such thatMfbdmd_a is generated about the center-of-gravity point G of the actualvehicle 1. In this case, for the right wheels W2 and W4,Fxfbdmd_2=Fxfbdmd_4=0 in the present embodiment.

Further, Fxfbdmd_1 and Fxfbdmd_3 related to the left wheels W1 and W3 inthis case are equal to Fxfb_1 and Fxfb_3 determined according to theaforesaid expressions 27a and 27c, respectively. Therefore, Fxfbdmd_1and Fxfbdmd_3 related to the left wheels W1 and W3 in the case whereMfbdmd_a>0 are respectively proportional to Mfbdmd_a. Consequently, therelationship between changes in Mfbdmd_a and changes in Fxfbdmd_1 andFxfbdmd_3 will be a proportional relationship. Further, in this case, asis obvious from the expression 24a and expression 27a, the front wheelgain GA1 related to the front wheel W1 is proportional to K1, becauseGA1=−(2/df)·K1_str·K1. And, this K1 is determined such that it changeson the basis of the actual front wheel side slip angle βf_act as thefront wheel gain adjustment parameter, as described above, so that thefront wheel gain GA1 will also change on the basis of βf_act. Hence,Fxfbdmd_1 is determined such that the relationship between changes inMfbdmd_a and changes in Fxfbdmd_1 will be a proportional relationshipand that the front wheel gain GA1 in the proportional relationshipchanges on the basis of βf_act used as the front wheel gain adjustmentparameter. Similarly, as is obvious from the expression 24c andexpression 27c, the rear wheel gain GA3 related to the rear wheel W3 isproportional to K3, because GA3=−(2/dr)·K3_str·K3. And, this K3 isdetermined such that it changes on the basis of the actual rear wheelside slip angle βr_act serving as the rear wheel gain adjustmentparameter, as described above, so that the rear wheel gain GA3 will alsochange on the basis of βr_act. Hence, Fxfbdmd_3 is determined such thatthe relationship between changes in Mfbdmd_a and changes in Fxfbdmd_3will be a proportional relationship and that the rear wheel gain GA3 inthe proportional relationship changes on the basis of βr_act serving asthe rear wheel gain adjustment parameter.

Further, the driving/braking forces of the right wheels W2 and W4 of theactual vehicle 1 are increased in the braking direction (to setFxfbdmd_2<0 and Fxfbdmd_4<0) if Mfbdmd_a<0, thereby determining the FBtarget n-th wheel brake driving/braking force Fxfbdmd_n(n=1, 2, 3, 4)such that Mfbdmd_a is generated about the center-of-gravity point G ofthe actual vehicle 1. In this case, for the left wheels W1 and W3,Fxfbdmd_1=Fxfbdmd_3=0 in the present embodiment.

Further, Fxfbdmd_2 and Fxfbdmd_4 related to the right wheels W2 and W4in this case are equal to Fxfb_2 and Fxfb_4 determined according to theexpressions 27b and 27d, respectively. Therefore, Fxfbdmd_2 andFxfbdmd_4 related to the right wheels W2 and W4 in the case whereMfbdmd_a<0 are respectively proportional to Mfbdmd_a. Furthermore, therelationship between changes in Mfbdmd_a and changes in Fxfbdmd_2 andFxfbdmd_4 will be a proportional relationship. Further, in this case, asis obvious from the expression 24b and the expression 27b, the frontwheel gain GA2 related to the front wheel W2 is proportional to K2,because GA2=(2/df)·K2_str·K2. And, this K2 is determined such that itchanges on the basis of the actual front wheel side slip angle βf_act asthe front wheel gain adjustment parameter, as described above, so thatthe front wheel gain GA2 will also change on the basis of βf_act. Hence,Fxfbdmd_2 is determined such that the relationship between changes inMfbdmd_a and changes in Fxfbdmd_2 will be a proportional relationshipand that the front wheel gain GA2 in the proportional relationshipchanges on the basis of βf_act serving as the front wheel gainadjustment parameter. Similarly, as is obvious from the expression 24dand the expression 27d, the rear wheel gain GA4 related to the rearwheel W4 is proportional to K4, because GA4=(2/dr)·K4_str·K4. And, thisK4 is determined such that it changes on the basis of the actual rearwheel side slip angle βr_act serving as the rear wheel gain adjustmentparameter, as described above, so that the rear wheel gain GA4 will alsochange on the basis of βr_act. Hence, Fxfbdmd_4 is determined such thatthe relationship between changes in Mfbdmd_a and changes in Fxfbdmd_4will be a proportional relationship and that the rear wheel gain GA4 inthe proportional relationship changes on the basis of βr_act serving asthe rear wheel gain adjustment parameter.

In either case, the n-th wheel distribution gain Kn(n=1, 2, 3, 4) isdetermined such that it virtually continuously changes according toβf_act or βr_act, thus preventing a situation wherein Fxfbdmd_ndiscontinuously changes.

In a situation wherein βf_act and βr_act take substantially the samevalue, as in the case where the actual vehicle 1 is in a normaltraveling mode when Mfbdmd_a>0, the ratio of the first wheeldistribution gain K1 and the third wheel distribution gain K2 associatedwith the front wheel W1 and the rear wheel W3 on the left side and alsoa front-to-rear wheel ratio, which is a ratio of the front wheel gainGA1 to the rear wheel gain GA3, monotonously change in response tochanges in the values of βf_act and βr_act. Similarly, in a situationwherein βf_act and βr_act take substantially the same value, as in thecase where the actual vehicle 1 is in the normal traveling mode whenMfbdmd_a<0, the ratio of the second wheel distribution gain K2 and thefourth wheel distribution gain K4 associated with the front wheel W2 andthe rear wheel W4 on the right side and also a front-to-rear wheelratio, which is a ratio of the front wheel gain GA2 to the rear wheelgain GA4, monotonously change in response to changes in the values ofβf_act and βr_act.

The following will explain the reason for determining the n-th wheeldistribution gain Kn(n=1, 2, 3, 4) on the basis of βf_act and βr_act inthe tendency described above.

First, if Mfbdmd_a>0, then the FB target n-th wheel brakedriving/braking force Fxfbdmd_n is determined such that thedriving/braking forces of the first wheel W1 and the third wheel W3,which are the left wheels of the actual vehicle 1, are increased in thebraking direction, as described above.

In this case, a situation wherein βf_act<0 and βr_act<0 is assumed. Insuch a situation, if it is assumed that K1 is set to a slightly largervalue (to cause Fxfbdmd_1 to increase in the braking direction) and K3is set to a slightly smaller value (to restrain Fxfbdmd_3 fromincreasing in the braking direction), then the lateral force of thefirst wheel W1 (this functions to generate a moment in the samedirection as Mfbdmd_a about the center-of-gravity point of the actualvehicle 1) decreases, whereas the lateral force of the third wheel W3(this functions to generate a moment in the opposite direction fromMfbdmd_a about the center-of-gravity point of the actual vehicle 1)slightly increases. For this reason, there is a danger that it becomesdifficult to adequately generate a moment in the positive direction (amoment about the yaw axis) required by Mfbdmd_a about thecenter-of-gravity point G of the actual vehicle 1. Hence, it has beendecided to determine the first wheel distribution gain K1 to be aslightly smaller value and to determine the third wheel distributiongain K3 to be a slightly larger value in the situation wherein βf_act<0and βr_act<0.

Another situation wherein βf_act>0 and βr_act>0 when Mfbdmd_a>0 will beassumed. In such a situation, if it is assumed that K1 is set to aslightly smaller value (consequently to restrain Fxfbdmd_1 fromincreasing in the braking direction) and K3 is set to a slightly largervalue (consequently to cause Fxfbdmd_3 to increase in the brakingdirection), then the lateral force of the first wheel W1 (this functionsto generate a moment in the opposite direction from Mfbdmd_a about thecenter-of-gravity point of the actual vehicle 1) slightly increases,whereas the lateral force of the third wheel W3 (this functions togenerate a moment in the same direction as Mfbdmd_a about thecenter-of-gravity point of the actual vehicle 1) decreases. For thisreason, there is a danger that it becomes difficult to adequatelygenerate a moment in the positive direction (a moment about the yawaxis) required by Mfbdmd_a about the center-of-gravity point G of theactual vehicle 1. Hence, it has been decided to determine the firstwheel distribution gain K1 to be a slightly larger value and todetermine the third wheel distribution gain K3 to be a slightly smallervalue in the situation wherein βf_act>0 and βr_act>0.

If Mfbdmd_a<0, then the FB target n-th brake driving/braking forceFxfbdmd_n is determined such that the driving/braking forces of thesecond wheel W2 and the fourth wheel W4, which are the right wheels ofthe actual vehicle 1, are increased in the braking direction, asdescribed above.

In this case, a situation wherein βf_act<0 and βr_act<0 is assumed. Insuch a situation, if it is assumed that K2 is set to a slightly smallervalue (to consequently restrain Fxfbdmd_2 from increasing in the brakingdirection) and K4 is set to a slightly larger value (to consequentlycause Fxfbdmd_4 to increase in the braking direction), then the lateralforce of the second wheel W2 (this functions to generate a moment in theopposite direction from Mfbdmd_a about the center-of-gravity point ofthe actual vehicle 1) increases, whereas the lateral force of the fourthwheel W4 (this functions to generate a moment in the same direction asMfbdmd_a about the center-of-gravity point of the actual vehicle 1)decreases. For this reason, there is a danger that it becomes difficultto adequately generate a moment in the negative direction (a momentabout the yaw axis) required by Mfbdmd_a about the center-of-gravitypoint G of the actual vehicle 1. Hence, it has been decided to determinethe second wheel distribution gain K2 to be a slightly larger value andto determine the fourth wheel distribution gain K4 to be a slightlysmaller value in the situation wherein βf_act<0 and βr_act<0.

Another situation wherein βf_act>0 and βr_act>0 when Mfbdmd_a<0 will beassumed. In such a situation, if it is assumed that K2 is set to aslightly larger value (consequently to cause Fxfbdmd_2 to increase inthe braking direction) and K4 is set to a slightly smaller value(consequently to restrain Fxfbdmd_4 from increasing in the brakingdirection), then the lateral force of the second wheel W2 (thisfunctions to generate a moment in the same direction as Mfbdmd_a aboutthe center-of-gravity point of the actual vehicle 1) decreases, whereasthe lateral force of the fourth wheel W4 (this functions to generate amoment in the opposite direction from Mfbdmd_a about thecenter-of-gravity point of the actual vehicle 1) increases. For thisreason, there is a danger that it becomes difficult to adequatelygenerate a moment in the negative direction (a moment about the yawaxis) required by Mfbdmd_a about the center-of-gravity point G of theactual vehicle 1. Hence, it has been decided to determine the secondwheel distribution gain K2 to be a slightly smaller value and todetermine the fourth wheel distribution gain K4 to be a slightly largervalue in the situation wherein βf_act>0 and βr_act>0.

Thus, determining the n-th wheel distribution gain Kn(n=1, 2, 3, 4) asdescribed above makes it possible to prevent a lateral force thatbecomes an obstacle in generating a moment of Mfbdmd_a in the yawdirection about the center-of-gravity point G of the actual vehicle 1from becoming excessive while at the same time preventing a lateralforce that is effective in generating a moment of Mfbdmd_a in the yawdirection about the center-of-gravity point G of the actual vehicle 1from becoming too small.

Moreover, by determining the n-th distribution gain Kn(n=1, 2, 3, 4) asdescribed above, the sum of a value of K1 and a value of K3 and the sumof a value of K2 and a value of K4, respectively, become substantiallyone in a situation wherein βf_act and βr_act agree or substantiallyagree with each other, as in the case where the actual vehicle 1 is in anormal circular turn mode or a normal straight travel mode. This meansthat if the braking device of the driving/braking device 3A is operatedfaithfully in accordance with the FB target n-th wheel brakedriving/braking force Fxfbdmd_n, then the gain of a transfer functionfrom Mfbdmd_a to a moment (a moment in the yaw direction) actuallygenerated about the center-of-gravity point G of the actual vehicle 1becomes substantially one (a moment in the yaw direction actuallygenerated becomes substantially equal to Mfbdmd_a).

Supplementally, there is a case where the difference between βf_act andβr_act increases in a transient motion situation or the like of theactual vehicle 1. And, in this case, the sum of a value of K1 and avalue of K3 and the sum of a value of K2 and a value of K4,respectively, considerably deviate from one. To solve this problem,preferably, after the values of K1 and K3 are determined as describedabove, the values of K1 and K3 are corrected while maintaining the ratioof the values at a constant level such that the sum of the correctedvalues of K1 and K3 becomes substantially one or becomes closer to onethan the sum of the values of K1 and K3 before the correction.Similarly, it is preferred that, after the values of K2 and K4 aredetermined as described above, the values of K2 and K4 are correctedwhile maintaining the ratio of the values at a constant level such thatthe sum of the corrected values of K2 and K4 becomes substantially oneor becomes closer to one than the sum of the values of K2 and K4 beforethe correction. To be more specific, for example, after the n-thdistribution gain Kn(n=1, 2, 3, 4) is determined according to the graphsof FIGS. 14( a) and (b), K1′, K2′, K3′ and K4′ are determined byK1′=K1/(K1+K3), K3′=K3/(K1+K3), K2′=K2/(K2+K4), and K4′=K4/(K2+K4).Then, K1′, K2′, K3′ and K4′ may be respectively re-determined as thevalues of K1, K2, K3 and K4.

In this example, the sum of K1 and K3 and the sum of K2 and K4 arealways maintained at one; however, the sums do not have to always agreewith one. Alternatively, the values of K1 to K4 may be corrected suchthat the sums take values within a range in the vicinity of one.Alternatively, K1 to K4 may be corrected such that the sum of K1 and k3and the sum of K2 and K4 approach further to one.

Further, in addition to determining the FB target n-th wheel brakedriving/braking force Fxfbdmd_n as described above, the actuatoroperation FB target value distribution processor 222 according to thepresent embodiment inputs the feedback yaw moment required value Mfbdmdto a processor 222 e so as to determine, by the processor 222 e, anactive steering FB target lateral force Fyfbdmd_f, which is a feedbacktarget value of the lateral force of the front wheels W1 and W2 by anoperation of the steering device 3B. The graph of the processor 222 e inthe figure is a graph showing a relationship between Mfbdmd andFyfbdmd_f, the values in the direction of the axis of abscissas relatedto the graph indicating the values of Mfbdmd, while the values in thedirection of the axis of ordinates indicating the values of Fyfbdmd_f.As shown in the graph, the processor 222 e basically determinesFyfbdmd_f such that Fyfbdmd_f monotonously increases as Mfbdmdincreases. In this case, Fyfbdmd_f is determined by using, for example,a map, from a value of Mfbdmd supplied to the processor 222 e.

Alternatively, Fyfbdmd_f may be determined by multiplying Mfbdmd by apredetermined gain. Further, Fyfbdmd_f may be determined on the basis ofMfbdmd within a range between a predetermined upper limit value (>0) anda predetermined lower limit value (<0).

Supplementally, the processing by the processor 222 e may be omittedregardless of whether the steering device 3B is an active steeringdevice or a mechanical steering device. When determining the activesteering FB target lateral force Fyfbdmd_f by the processing of theprocessor 222 e and manipulating the operation of the steering device 3Bon the basis of the determined Fyfbdmd_f, it is further preferable todetermine Fxfbdmd_n(n=1, 2, 3, 4) and Fyfbdmd_f such that the sum of amoment in the yaw direction to be generated about the center-of-gravitypoint G of the actual vehicle 1 by the FB target n-th wheel brakedriving/braking force Fxfbdmd_n (n=1, 2, 3, 4) and a moment in the yawdirection generated about the center-of-gravity point G of the actualvehicle 1 by the active steering FB target lateral force Fyfbdmd_f issubstantially equal to the aforesaid feedback yaw moment basic requiredvalue Mfbdmd. For example, the active steering FB target lateral forceFyfbdmd_f may be determined on the basis of a difference between Mfbdmdand Mfbdmd_a. In this case, it is desirable to determine Fyfbdmd_f suchthat a moment in the yaw direction that is substantially equal to Mfbdmdis generated about the center-of-gravity point G of the actual vehicle 1by Fyfbdmd_f when Mfbdmd_a=0.

The above has explained the details of the processing by the actuatoroperation FB target value determiner 20 b in the present embodiment.This processing determines the FB target n-th wheel brakedriving/braking force Fxfbdmd_n(n=1, 2, 3, 4) or Fxfbdmd_n(n=1, 2, 3, 4)and the active steering FB target lateral force Fyfbdmd_f as theactuator operation FB target value such that Mfbdmd is approximated tozero (consequently to approximate the state amount errors γerr and βerrto zero), as described above.

The limiter 222 d _(—) n(n=1, 2, 3, 4) may output, as Fxfbdmd_n, a valueobtained by limiting Fxfb_n input thereto to not more than apredetermined positive upper limit value, which is slightly larger thanzero. For example, if Fxfb_n is a value that is the upper limit value orless, then Fxfb_n is directly output as Fxfbdmd_n without processing it,or if Fxfb_n takes a positive value that is larger than the upper limitvalue, then the upper limit value is output as Fxfbdmd_n. In this case,Fxfbdmd_n of a positive value provides a feedback control input thatfunctions to decrease the magnitude of the driving/braking force of then-th wheel Wn in the braking direction by the braking device.

Further, for each wheel Wn(n=1, 2, 3, 4), the processing from theprocessor 222 a _(—) n to the limiter 222 d _(—) n (the processing fordetermining Fxfbdmd_n on the basis of Mfbdmd_a and δf_act or δr_act andβf_act or βr_act), or the processing from the processor 222 b _(—) n tothe limiter 222 d _(—) n (the processing for determining Fxfbdmd_n onthe basis of Fxfullfbdmd_n and δf_act or δr_act and βf_act or βr_act),or the processing from the processor 222 c _(—) n to the limiter 222 d_(—) n (the processing for determining Fxfbdmd_n on the basis of anoutput of the processor 222 b _(—) n and βf_act or βr_act), or theprocessing that combines two or more portions of the processing from theprocessor 222 a _(—) n to the limiter 222 d _(—) n (e.g., the processingfrom the processor 222 b _(—) n to the processor 222 c _(—) n) may bechanged to determine an output by using a map or a function expressionfrom input values necessary for such processing.

For instance, to carry out the processing from the processor 222 c _(—)n to the limiter 222 d _(—) n by using a map, a map for the first wheelmay be set as shown in, for example, FIGS. 15( a) to (e), and a map forthe third wheel may be set as shown in, for example, FIGS. 16( a) to(e). In this case, the graphs in FIGS. 15( a) to (e), respectively, showthe relationships between outputs of the processor 222 b_1(=Fxfullfbdmd_1·K1_str) and Fxfbdmd_1 in association with a plurality ofrepresentative types of values of βf_act, the individual values beingshown in terms of the values in the direction of the axis of abscissasof the graphs and the values in the direction of the axis of ordinates.Further, the graphs in FIGS. 16( a) to (e), respectively, show therelationships between outputs of the processor 222 b_3(=Fxfullfbdmd_3·K3_str) and Fxfbdmd_3 in association with a plurality ofrepresentative types of values of βr_act, the individual values beingshown in terms of the values in the direction of the axis of abscissasof the graphs and the values in the direction of the axis of ordinates.In FIG. 15, regarding the values of βf_act, “βf−−” means a negativevalue having a relatively large absolute value, “βf−” means a negativevalue having a relatively small absolute value, “βf+” means a positivevalue having a relatively small absolute value, and “f++” means apositive value having a relatively large absolute value. Similarly, inFIG. 16, regarding the values of βr_act, “βr−−” means a negative valuehaving a relatively large absolute value, “βr−” means a negative valuehaving a relatively small absolute value, “βr+” means a positive valuehaving a relatively small absolute value, and “βr++” means a positivevalue having a relatively large absolute value.

Although not shown, a map for the second wheel may be set such that therelationship between outputs of the processor 222 b_2(=Fxfullfbdmd_2·K2_str) and Fxfbdmd_2 will be the same at each value ofβf_act as that in the map for the first wheel associated with the valuesobtained by reversing the signs of the values (e.g., the relationshipbetween an output of the processor 222 b_2 when βf_act=βf−(=Fxfullfbdmd_2·K2_str) and Fxfbdmd_2 will be the same as therelationship between an output of the processor 222 b_1 when βf_act=βf+and Fxfbdmd_1 (the relationship shown by the graph of FIG. 15( c))).Similarly, although not shown, a map for the fourth wheel may be setsuch that the relationship between outputs of the processor 222 b_4(=Fxfullfbdmd_4·K4_str) and Fxfbdmd_4 will be the same at each value ofβr_act as that in the map for the third wheel associated with the valuesobtained by reversing the signs of the values (e.g., the relationshipbetween an output of the processor 222 b_4 when βr_act=βr−(=Fxfullfbdmd_4·K4_str) and Fxfbdmd_4 will be the same as therelationship between an output of the processor 222 b_3 when βr_act=βr+and Fxfbdmd_3 (the relationship shown by the graph of FIG. 16( c))).

In this example, if an output of the processor 222 b _(—) n(n=1, 2, 3,4) is a value of zero or less, then Fxfbdmd_n is determined in the samemanner as that shown in FIG. 12 described above. Meanwhile, if an outputof the processor 222 b _(—) n(n=1, 2, 3, 4) is a positive value, thenFxfbdmd_n takes a positive value within a range of relatively smallvalues as with the case where the upper limit value in the limiter 222 d_(—) n is set to a positive value as described above.

Supplementally, both the processors 222 b_3 and 222 b_4 associated withthe third wheel W3 and the fourth wheel W4 share the same input valuesand output values; therefore, carrying out the processing from theprocessor 223 c_3 to the limiter 222 d_3 and the processing from theprocessor 222 c_4 to the limiter 222 d_4 on the third wheel W3 and thefourth wheel W4 by using the maps as described above is equivalent tocarrying out the processing from the processor 222 b_3 to the limiter222 d_3 and the processing from the processor 222 b_4 to the limiter 222d_4 by using the maps.

Further, as the front wheel gain adjustment parameter for determining(whereby to manipulate the front wheel gains GA1 and GA2) the n-th wheeldistribution gain Kn(n=1, 2) related to the front wheels W1 and W2, thefollowing may be used besides βf_act.

For example, in place of βf_act, the detected values or the estimatedvalues of the side slip velocities of the front wheels W1 and W2 of theactual vehicle 1 (components in the direction of the rotational axes ofthe front wheels W1 and W2 in the advancing velocity vectors of thefront wheels W1 and W2) or the detected values or the estimated valuesof the lateral accelerations of the front wheels W1 and W2 (lateralcomponents of the acceleration vectors of the front wheels W1 and W2)may be used as the front wheel gain adjustment parameters. Incidentally,the side slip velocities or the lateral accelerations of the frontwheels W1 and W2 are examples of the state amounts related to lateralmotions of the front wheels W1 and W2, as with βf_act. These side slipvelocities and the lateral accelerations may be the detected values orthe estimated values of each of the front wheels W1 and W2;alternatively, however, the means values thereof or the detected valuesor the estimated values of either one of the front wheels W1 and W2 maybe used.

Alternatively, a detected value or an estimated value of an actual sideslip angle at a predetermined position of a front portion of the actualvehicle 1 (e.g., a central position on the axle of the front wheels W1and W2), or a detected value or an estimated value of the side slipvelocity at the predetermined position (a lateral component of theadvancing velocity vector at the predetermined position), or a detectedvalue or an estimated value of the lateral acceleration at thepredetermined position (a lateral component of the acceleration vectorat the predetermined position) may be used as the front wheel gainadjustment parameter. The side slip angle, the side slip velocity, andthe lateral acceleration at the predetermined position are examples ofthe state amounts related to a lateral motion at the predeterminedposition.

Alternatively, the detected values or the estimated values of thelateral forces of the front wheels W1 and W2 may be used as the frontwheel gain adjustment parameters. The lateral forces may take a detectedvalue or an estimated value for each of the front wheels W1 and W2 ormay take a mean value thereof or a detected value or an estimated valueon either one of the front wheels W1 and W2.

Regardless of which of the aforesaid front wheel gain adjustmentparameters may be used, the relationship between a front wheel gainadjustment parameter and the n-th wheel distribution gain Kn (n=1, 2)may be set in the same manner as that for the relationship betweenβf_act and K1, K2.

Alternatively, a parameter having correlativity with one of the stateamounts (such as βf_act) related to the lateral motions of the frontwheels W1 and W2 of the actual vehicle 1 as described above, a stateamount related to a lateral motion at a predetermined position of afront portion of the actual vehicle 1, and the lateral forces of thefront wheels W1 and W2 may be used as a front wheel gain adjustmentparameter. For instance, any parameter that is substantiallyproportional to a state amount related to the lateral motion or adetected value or an estimated value of a lateral force may be used as afront wheel gain adjustment parameter. Further, a state amount relatedto the lateral motion or one or more parameters that define the value ofa lateral force may be used as the front wheel gain adjustmentparameters. For example, βf_act is basically defined on the basis of theactual vehicle center-of-gravity point side slip angle βact, the actualyaw rate γact, the actual traveling velocity Vact, and the actual frontwheel steering angle δf_act (refer to the expression 02a), and βf_actcan be expressed as a function of βact, γact, Vact, and δf_act.Accordingly, these βact, γact, Vact, and δf_act may be used as the frontwheel gain adjustment parameters in order to determine the n-th wheeldistribution gain Kn(n=1, 2) associated with the front wheels W1 and W2according to a map or a function expression on the basis of theaforesaid front wheel gain adjustment parameters. More specifically, forexample, the aforesaid relationship between βf_act and the first wheeldistribution gain K1 and the second wheel distribution gain K2 (therelationship shown by the graph in FIG. 14( a) described above) isconverted beforehand into a relationship between βact, γact, Vact andδf_act and K1 and K2 on the basis of an expression which has replacedβf_d, βd, γd, Vd and δf_d of the expression 02a related to the modelvehicle by βf_act, βact, γact, Vact and δf_act, respectively. Then,based on the relationship obtained by the conversion, K1 and K2 may bedetermined according to βact, γact, Vact and δf_act.

Similarly to the above, the following may be used besides βr_act as afront wheel gain adjustment parameter for determining (so as tomanipulate the rear wheel gains GA3 and GA4) the n-th wheel distributiongain Kn(n=3, 4) associated with the rear wheels W3 and W4.

For example, in place of βr_act, the detected values or the estimatedvalues of the side slip velocities of the rear wheels W3 and W4 of theactual vehicle 1 (components in the direction of the rotational axes ofthe rear wheels W3 and W4 in the advancing velocity vectors of the rearwheels W3 and W4) or the detected values or the estimated values of thelateral accelerations of the rear wheels W3 and W4 (lateral componentsof the acceleration vectors of the rear wheels W3 and W4) may be used asthe rear wheel gain adjustment parameters. Incidentally, the side slipvelocities or the lateral accelerations of the rear wheels W3 and W4 areexamples of the state amounts related to lateral motions of the rearwheels W3 and W4, as with βr_act. These side slip angles, the side slipvelocities and the lateral accelerations may be a detected value or anestimated value of each of the rear wheels W3 and W4; alternatively,however, a means value thereof or a detected value or an estimated valueof either one of the rear wheels W3 and W4 may be used.

Alternatively, a detected value or an estimated value of a side slipangle at a predetermined position of a rear portion of the actualvehicle 1 (e.g., a central position on the axle of the rear wheels W3and W4), or a detected value or an estimated value of a side slipvelocity at the predetermined position (a lateral component of theadvancing velocity vector at the predetermined position), or a detectedvalue or an estimated value of a lateral acceleration at thepredetermined position (a lateral component of the acceleration vectorat the predetermined position) may be used as the rear wheel gainadjustment parameter. The side slip angle, the side slip velocity, andthe lateral acceleration at the predetermined position are examples ofthe state amounts related to a lateral motion at the predeterminedposition.

Alternatively, the detected values or the estimated values of thelateral forces of the rear wheels W3 and W4 of the actual vehicle 1 maybe used as the rear wheel gain adjustment parameters. The lateral forcesmay take a detected value or an estimated value for each of the rearwheels W3 and W4 or may take a mean value thereof or a detected value oran estimated value on either one of the rear wheels W3 and W4.

Regardless of which of the aforesaid rear wheel gain adjustmentparameters may be used, the relationship between the rear wheel gainadjustment parameter and the n-th wheel distribution gain Kn (n=3, 4)may be set in the same manner as that for the relationship betweenβr_act and K3, K4.

Alternatively, a parameter having correlativity with one of the stateamounts (such as βr_act) related to the lateral motions of the rearwheels W3 and W4 of the actual vehicle 1 as described above, a stateamount related to a lateral motion at a predetermined position of a rearportion of the actual vehicle 1, and the lateral forces of the rearwheels W3 and W4 may be used as a rear wheel gain adjustment parameter.For instance, any parameter that is substantially proportional to astate amount related to the lateral motion or a detected value or anestimated value of a lateral force may be used as a rear wheel gainadjustment parameter. Further, a state amount related to the lateralmotion or one or more parameters that define the value of a lateralforce may be used as the rear wheel gain adjustment parameters. Forexample, βr_act is basically defined on the basis of the actual vehiclecenter-of-gravity point side slip angle βact, the actual yaw rate γact,and the actual traveling velocity Vact (refer to the aforesaidexpression 02b), and βr_act can be expressed as a function of βact,γact, and Vact. Accordingly, these βact, γact, Vact may be used as therear wheel gain adjustment parameters in order to determine the n-thwheel distribution gain Kn(n=3, 4) associated with the rear wheels W3and W4 according to a map or a function expression on the basis of therear wheel gain adjustment parameters. More specifically, for example,the aforesaid relationship between βr_act and the third wheeldistribution gain K3 and the fourth wheel distribution gain K4 (therelationship shown by the graph in FIG. 14( b) described above) isconverted beforehand into a relationship between βact, γact, and Vactand K3 and K4 on the basis of an expression which has replaced βr_d, βd,γd, and Vd of the expression 02b related to the model vehicle by βr_act,βact, γact, and Vact, respectively. Then, based on the relationshipobtained by the conversion, K3 and K4 may be determined according toβact, γact, and Vact.

Further, instead of using the state amounts related to the lateralmotions of the front wheels W1 and W2 of the actual vehicle 1, the stateamount related to the lateral motion at the predetermined position ofthe front portion of the actual vehicle 1, the lateral forces of thefront wheels W1 and W2 of the actual vehicle 1, and a parameter havingcorrelativity with any one of these state amounts and the lateral forcesas the front wheel gain adjustment parameters, as described above, thestate amounts or lateral forces or parameters corresponding thereto inthe model vehicle on the reference dynamic characteristics model 16 maybe used as the front wheel gain adjustment parameters. For instance,βf_d of the model vehicle in place of βf_act may be used as the frontwheel gain adjustment parameter to determine the first wheeldistribution gain K1 and the second wheel distribution gain K2.Similarly, instead of using the state amounts related to the lateralmotions of the rear wheels W3 and W4 of the actual vehicle 1, the stateamount related to the lateral motion at the predetermined position ofthe rear portion of the actual vehicle 1, the lateral forces of the rearwheels W3 and W4 of the actual vehicle 1, and a parameter havingcorrelativity with any one of these state amounts and the lateral forcesas the rear wheel gain adjustment parameters, the state amounts orlateral forces or parameters corresponding thereto in the model vehicleon the reference dynamic characteristics model 16 may be used as therear wheel gain adjustment parameters. For instance, βr_d of the modelvehicle in place of βr_act may be used as the rear wheel gain adjustmentparameter to determine the third wheel distribution gain K3 and thefourth wheel distribution gain K4.

Alternatively, a composite value of a state amount related to a lateralmotion of the front wheels W1 and W2 or at a predetermined position of afront portion of the actual vehicle 1 and a state amount related to alateral motion of the front wheel Wf or at a predetermined position ofthe front portion of the model vehicle (the same type of state amount asthat of the state amount of the actual vehicle 1), or a composite valueof a lateral force of the front wheels W1 and W2 of the actual vehicle 1and a lateral force of the front wheel Wf of the model vehicle may beused as the front wheel gain adjustment parameter. Similarly, acomposite value of a state amount related to a lateral motion of therear wheels W3 and W4 or at a predetermined position of a rear portionof the actual vehicle 1, and a state amount related to a lateral motionof the rear wheel Wr or at a predetermined position of the rear portionof the model vehicle (the same type of state amount as that of the stateamount of the actual vehicle 1), or a composite value of a lateral forceof the rear wheels W3 and W4 of the actual vehicle 1 and a lateral forceof the rear wheel Wr of the model vehicle may be used as the rear wheelgain adjustment parameter. For example, the first wheel distributiongain K1 and the second wheel distribution gain K2 may be determined onthe basis of a weighted mean value of βf_act of the actual vehicle 1 andβf_d of the model vehicle, and the third wheel distribution gain K3 andthe fourth wheel distribution gain K4 may be determined on the basis ofa weighted mean value of βr_act of the actual vehicle 1 and βr_d of themodel vehicle. In this case, the weights involved in the weighted meanvalues may be provided with a frequency characteristic (e.g., afrequency characteristic functioning as a phase compensating element).

Alternatively, the first temporary values of the respective n-th wheeldistribution gains Kn(n=1, 2) related to the front wheels W1 and W2 maybe determined on the basis of a state amount related to a lateral motionof the front wheels W1 and W2 or at a predetermined position of thefront portion of the actual vehicle 1 or a lateral force of the frontwheels W1 and W2 of the actual vehicle 1, and the second temporaryvalues of the respective n-th wheel distribution gains Kn(n=1, 2)related to the front wheels W1 and W2 may be determined on the basis ofa state amount related to a lateral motion of the front wheel Wf or at apredetermined position of the front portion of the model vehicle or alateral force of the front wheel Wf of the model vehicle, and acomposite value of the weighed mean value or the weighted mean values orthe like of the first temporary values and the second temporary valuesmay be determined as the n-th wheel distribution gain Kn(n=1, 2). Forexample, the first temporary value of K1 related to the first wheel W1is determined on the basis of βf_act as indicated by the graph shown inFIG. 14( a) described above and the second temporary value of K1 isdetermined on the basis of βf_d in the same manner as that for the firsttemporary value. In this case, the tendency of changes in the secondtemporary value relative to βf_d may be the same as the tendency ofchanges in the first temporary value relative to βf_act. Then, a weighedmean value of these first temporary value and second temporary value isdetermined as the first wheel distribution gain K1. The same applies tothe second wheel distribution gain K2.

Similarly, the first temporary values of the respective n-th wheeldistribution gains Kn(n=3, 4) related to the rear wheels W3 and W4 maybe determined on the basis of a state amount related to a lateral motionof the rear wheels W3 and W4 or at a predetermined position of the rearportion of the actual vehicle 1 or a lateral force of the rear wheels W3and W4 of the actual vehicle 1, and the second temporary values of then-th wheel distribution gains Kn(n=3, 4) related to the rear wheels W3and W4 may be determined on the basis of a state amount related to alateral motion of the rear wheel Wr or at a predetermined position ofthe rear portion of the model vehicle or a lateral force of the rearwheel Wr of the model vehicle, and a composite value of the weighed meanvalues or the weighted mean values or the like of the first temporaryvalues and the second temporary values may be determined as the n-thwheel distribution gain Kn(n=3, 4). For example, the first temporaryvalue of K3 related to the third wheel W3 is determined on the basis ofβr_act as indicated by the graph shown in FIG. 14( b) described aboveand the second temporary value of K3 is determined on the basis of βr_din the same manner as that for the first temporary value. In this case,the tendency of changes in the second temporary value relative to βr_dmay be the same as the tendency of changes in the first temporary valuerelative to βr_act. Then, a weighed mean value of these first temporaryvalue and second temporary value is determined as the third wheeldistribution gain K3. The same applies to the fourth wheel distributiongain K4.

Further desirably, the value of the n-th wheel distribution gain Kn(n=1,2, 3, 4) is determined such that the value is not only changed accordingto a front wheel gain adjustment parameter or a rear wheel gainadjustment parameter, such as βf_act or βr_act, but also changedaccording to the estimated friction coefficient μestm. For example, whendetermining the n-th wheel distribution gain Kn on the basis of βf_actor βr_act, as described above in relation to the present embodiment, K1is desirably determined such that the first wheel distribution gain K1when βf_act is a negative value having a large absolute value is furtherdecreased as μestm is decreased. Further, K3 is desirably determinedsuch that the third wheel distribution gain K3 when βr_act is a positivevalue having a large absolute value is further decreased as μestm isdecreased. Similarly, K2 is desirably determined such that the secondwheel distribution gain K2 when βf_act is a positive value having alarge absolute value is further decreased as μestm is decreased.Further, K4 is desirably determined such that the fourth wheeldistribution gain K4 when βr_act is a negative value having a largeabsolute value is further decreased as μestm is decreased. This isbecause, as μestm decreases, the lateral force of the n-th wheel Wnconsiderably reduces when the driving/braking force of the n-th wheelWn(n=1, 2, 3, 4) in the braking direction is increased.

Further, a value (a value set on the basis of a front wheel gainadjustment parameter or a rear wheel gain adjustment parameter, such asβf_act or βr_act) of the n-th wheel distribution gain Kn(n=1, 2, 3, 4)may be adjusted also on the basis of an actual ground contact load ofthe n-th wheel (a detected value or an estimated value of atranslational force, which is in the vertical direction or a directionperpendicular to a road surface, of a road surface reaction force actingon the n-th wheel). In this case, the value of the n-th wheeldistribution gain Kn is desirably determined such that it decreases asthe actual ground contact load of the n-th wheel Wn decreases.

Alternatively, when the actual ground contact load of each n-th wheel Wnis expressed by Fzact_n(n=1, 2, 3, 4) and the total sum thereof isexpressed by ΣFzact(=Fzact_1+Fzact_2+Fzact_3+Fzact_4), the values of then-th wheel distribution gains K1 and K2 related to the front wheels W1and W2 may be adjusted on the basis of the sum of the actual groundcontact loads of the front wheels W1 and W2 (=Fzact_1+Fzact_2) or may beadjusted on the basis of a ratio of the sum with respect to ΣFzact(=(Fzact_1+Fzact_2)/ΣFzact). Similarly, the n-th wheel distributiongains K3 and K4 related to the rear wheels W3 and W4 may be adjusted onthe basis of the sum of the actual ground contact loads of the rearwheels W3 and W4 (=Fzact_3+Fzact_4) or may be adjusted on the basis of aratio of the sum with respect to ΣFzact (=(Fzact_3+Fzact_4)/ΣFzact).Alternatively, the value of each n-th wheel distribution gain Kn(n=1, 2,3, 4) may be adjusted on the basis of the ratio of the actual groundcontact load of each n-th wheel Wn with respect to ΣFzact(=Fzact_n/ΣFzact).

Further, in the present embodiment, as the feedback control input to thebraking device of the driving/braking device 3A (as the actuatoroperation FB target value), the FB target n-th wheel brakedriving/braking force Fxfbdmd_n(n=1, 2, 3, 4) has been determined;alternatively, however, instead of Fxfbdmd_n, a target slip ratio ofeach wheel Wn(n=1, 2, 3, 4) by the braking device may be determined orboth the target slip ratio and Fxfbdmd_n may be determined.

The feedback yaw moment basic required value Mfbdmd may be determinedsuch that Mfbdmd not only causes the state amount errors γerr and βerrto approximate zero but also causes the deviation amounts γover andβover determined by the γβ limiter 202 of the virtual external forcedeterminer 20 a to approximate zero (thereby to restrain the γda and βdafrom deviating from their permissible ranges [γdamin, γdamax] and[βdamin, βdamax], respectively). For example, Mfbdmd may be determinedaccording to expression 28a given below by using appropriatecoefficients Kfbdmd1 to Kfbdmd4.

$\begin{matrix}{{Mfbdmd} = {{{Kfbdmd}\; {1 \cdot \gamma}\; {err}} + {{Kfbdmd}\; {2 \cdot \beta}\; {err}} - {{Kfdbdmd}\; {3 \cdot \gamma}\mspace{11mu} {over}} - {{kfbdmd}\; {4 \cdot \beta}\mspace{11mu} {over}}}} & {{Expression}\mspace{14mu} 28a}\end{matrix}$

Determining Mfbdmd according to this expression 28a is equivalent todetermining Mfbdmd by correcting the temporary value of Mfbdmddetermined by the feedback control law for approximating the stateamount errors γerr and βerr to zero (the sum of the first term and thesecond term of the right side of expression 28a) such that the deviationamounts γover and βover are approximated to zero.

Alternatively, the aforesaid dead-zone excess feedback yaw momentrequired value Mfbdmd_a, which is the value obtained by passing Mfbdmddetermined to bring the state amount errors γerr and βerr close to zeroaccording to the expression 23 through the dead-zone processor 221, maybe corrected by expression 28b given below (an expression that usesMfbdmd_a in place of the value of the sum of the first term and thesecond term of the right side of the above expression 28a) to determinea value Mfbdmd_a′ and this Mfbdmd_a′ may be again used as Mfbdmd_a. Inother words, the value obtained by passing Mfbdmd through the dead-zoneprocessor 221 is defined as a temporary value of Mfbdmd_a, and Mfbdmd_amay be determined by correcting the temporary value such that thedeviation amounts γover and βover approximate zero.

Mfbdmd_(—) a′=Mfbdmd_(—) a−Kfbdmd3·γover−Kfbdmd4·βover   Expression 28b

Supplementally, according to the present embodiment, the virtualexternal force temporary values Mvirtmp and Fvirtmp are manipulated toapproximate γover and βover to zero by the γβ limiter 202, as describedabove, thereby determining the virtual external forces Mvir and Fvir.This alone restrains γd and βd of the model vehicle from deviating fromtheir permissible ranges [γdamin, γdamax] and [βdamin, βdamax],respectively, when they change. Accordingly, the actuator operation FBtarget value changes such that γact and βact of the actual vehicle 1 arebrought close to γd and βd, respectively. Therefore, even when theactuator operation FB target value is determined such that only γerr andβerr are brought close to zero, the γact and βact can be alsoconsequently restrained from deviating from the permissible ranges[γdamin, γdamax] and [βdamin, βdamax]. However, determining Mfbdmd orMfbdmd_a (so as to determine the actuator operation FB target value)such that γover and βover are also brought close to zero in addition toγerr and βerr as described above makes it possible to furthereffectively restrain the γact and βact from deviating from thepermissible ranges [γdamin, γdamax] and [βdamin, βdamax], respectively.

Further, if Mfbdmd or Mfbdmd_a is determined such that γover and βoverare also brought close to zero, in addition to γerr and βerr, asdescribed above, then it is not always necessary to determine thevirtual external forces Mvir and Fvir such that γover and βover arebrought close to zero; instead, the virtual external forces Mvir andFvir may be determined so as simply to bring γerr and βerr close tozero. In this case, the virtual external force temporary values Mvirtmpand Fvirtmp determined by the virtual external force temporary valuedeterminer 201 may be directly determined as the virtual external forcesMvir and Fvir, respectively. And, the processing other than theprocessing for determining Mfbdmd or Mfbdmd_a and the processing fordetermining the virtual external forces Mvir and Fvir may be the same asthat in the present embodiment. This also makes it possible to determinethe actuator operation FB target value such that γact and βact arerestrained from deviating from the permissible ranges [γdamin, γdamax]and [βdamin, βdamax], respectively. Even in this case, the virtualexternal forces Mvir and Fvir are determined such that the state amounterrors γerr and βerr approximate zero, so that the γd and βd areconsequently determined such that the γd and βd of the model vehicle arerestrained from deviating from the permissible ranges [γdamin, γdamax]and [βdamin, βdamax], respectively.

Incidentally, in the case where the expression 28b is used to determineMfbdmd_a (=Mfbdmd_a′), the sum of the second term and the third term ofthe right side of the expression 28b corresponds to the feedbackauxiliary required amount in the present invention. In this case, ifMfbdmd exists in the dead zone of the dead-zone processor 221, thenMfbdmd_a of the right side of expression 28a takes zero, which is thepredetermined value in the dead zone, so that the FB target n-th wheelbrake driving/braking force Fxfbdmd_n as an actual vehicle actuatoroperation control input will be determined on the basis of Mfbdmd_a′obtained by correcting the zero on the basis of the feedback auxiliaryrequired amount. If Mfbdmd does not exist in the dead zone of thedead-zone processor 221, then Mfbdmd_a of the right side of expression28a means an excess of Mfbdmd from the dead zone; therefore,consequently, the FB target n-th wheel brake driving/braking forceFxfbdmd_n as an actual vehicle actuator operation control input will bedetermined on the basis of Mfbdmd_a′ obtained by correcting Mfbdmd onthe basis of at least the feedback auxiliary required amount.

[About the FF Law]

The processing by the FF law 22 will now be explained in detail withreference to FIG. 17. FIG. 17 is a functional block diagram showing theprocessing by the FF law 22.

As described above, according to the present embodiment, a feedforwardtarget value determined by the FF law 22 (a basic target value of theactuator devices 3 on the basis of drive operation inputs) includes thefeedforward target values of the driving/braking forces of the wheels W1to W4 of the actual vehicle 1 by the braking device of thedriving/braking device 3A (hereinafter referred to as the FF target n-thwheel brake driving/braking forces (n=1, 2, 3, 4)), the feedforwardtarget values of the driving/braking forces of the driving wheels W1 andW2 of the actual vehicle 1 by the driving system of the driving/brakingdevice 3A (hereinafter referred to as the FF target n-th wheel drivingsystem driving/braking forces (n=1, 2)), the feedforward target value ofa reduction gear ratio (change gear ratio) of the speed change gear ofthe driving/braking device 3A (hereinafter referred to as the FF targettransmission reduction gear ratio), and the feedforward target values ofthe steering angles of the steering control wheels W1 and W2 of theactual vehicle 1 by the steering device 3B (hereinafter referred to asthe FF target front wheel steering angle δf_ff).

As shown in FIG. 17, the FF target front wheel steering angle δf_ff isdetermined by a processor 230 on the basis of the steering angle Θh (oron the basis of Θh and Vact) of drive operation inputs. In FIG. 17, itis assumed that the steering device 3B is the actuator-driven steeringdevice. In this case, the processor 230 determines the FF target frontwheel steering angle δf_ff by the same processing as the processing bythe processor 14 a of the reference manipulated variable determiner 14.More specifically, the steering angle Θh is divided by a predeterminedoverall steering ratio_(is) or an overall steering ratio_(is) set on thebasis of Vact thereby to determine δf_ff. The value of δf_ff thusdetermined is the same as the value of the unlimited front wheelsteering angle δf_unltd determined by the processor 14 a of thereference manipulated variable determiner 14.

If the steering device 3B is the actuator-assisted steering device or amechanical steering device, then it is unnecessary to determine δf_ff.Alternatively, δf_ff may be always set to zero. However, if the steeringdevice 3B is the actuator-assisted steering device and has a functionfor correcting, on the basis of Vact, the steering angles of the frontwheels W1 and W2 mechanically determined on the basis of the steeringangle Θh, then the correction may be determined on the basis of Vact andthe obtained correction may be determined as δf_ff.

Supplementally, if the steering device 3B is an actuator-assistedsteering device, then the basic steering angles of the front wheels W1and W2 (the basic values of δf_act) are mechanically determined on thebasis of the steering angle Θh, so that δf_ff has a meaning as thefeedforward target values of the correction amounts of the steeringangles of the front wheels W1 and W2 by an actuator.

Further, the FF target n-th wheel brake driving/braking forces (n=1, 2,3, 4) are respectively determined by processors 231 a _(—) n(n=1, 2, 3,4) on the basis of a brake pedal manipulated variable of drive operationinputs. The graphs shown in the processors 231 a _(—) n in the figurerespectively are graphs illustrating the relationship between brakepedal manipulated variables and the FF target n-th wheel brakedriving/braking forces (n=1, 2, 3, 4), the values in the direction ofthe axis of abscissas in the graphs indicating the values of the brakepedal manipulated variables, while the values in the direction of theaxis of ordinates indicating the FF target n-th wheel brakedriving/braking forces. As shown in the graphs of the figure, the FFtarget n-th wheel brake driving/braking forces (<0) are basicallydetermined such that the magnitudes (absolute values) thereofmonotonously increase as the brake pedal manipulated variable increases.In the illustrated examples, the FF target n-th wheel brakedriving/braking forces are set such that they are saturated when a brakepedal manipulated variable exceeds a predetermined amount (theincreasing rate of the absolute value of the FF target n-th wheel brakedriving/braking force relative to an increase in the brake pedalmanipulated variable approaches zero or reaches zero), therebypreventing the magnitude of the FF target n-th wheel brakedriving/braking force from becoming excessive.

The FF target n-th wheel driving system driving/braking forces (n=1, 2)and the FF target transmission reduction gear ratio are determined by adriving system actuator operation FF target value determiner 232 on thebasis of an accelerator (gas) pedal manipulated variable, a shift leverposition, and Vact of drive operation inputs. The processing by thedriving system actuator operation FF target value determiner 232 may bethe same method for determining a driving force transmitted from anengine to driving wheels and the reduction gear ratio of a speed changegear on the basis of an accelerator (gas) pedal manipulated variable,Vact, and the shift lever position of the speed change gear in apublicly known regular car; so that detailed explanation thereof in thepresent description will be omitted.

The above has described the specific processing by the FF law 22 in thepresent embodiment.

[About the Actuator Operation Target Value Synthesizer]

The processing by the actuator operation target value synthesizer 24will now be explained in detail. FIG. 18 is a functional block diagramshowing the processing by the actuator operation target valuesynthesizer 24.

Referring to the figure, regarding the first wheel W1, the actuatoroperation target value synthesizer 24 determines, by an adder 240, thesum of the FF target first wheel brake driving/braking force of theactuator operation FF target value and the FF target first wheel drivingsystem driving/braking force. Then, the sum is input as an FF totaltarget first wheel driving/braking force FFtotal_1 into an optimumtarget first driving/braking force determiner 241 a _(—) 1. Further, thesum of this FFtotal_1 and the FB target first wheel brakedriving/braking force Fxfbdmd_1 of the actuator operation FB targetvalue is determined by an adder 242. Then, the sum is input as anunlimited target first wheel driving/braking force Fxdmd_1 into theoptimum target first driving/braking force determiner 241 a_1.

Regarding the second wheel W2, the actuator operation target valuesynthesizer 24 determines, by an adder 243, the sum of the FF targetsecond wheel brake driving/braking force of the actuator operation FFtarget value and the FF target second wheel driving systemdriving/braking force. Then, the sum is input as an FF total targetsecond wheel driving/braking force FFtotal_2 into an optimum targetsecond driving/braking force determiner 241 a_2. Further, the sum ofthis EFtotal_2 and the FB target second wheel brake driving/brakingforce Fxfbdmd_2 of the actuator operation FB target value is determinedby an adder 244. Then, the sum is input as an unlimited target secondwheel driving/braking force Fxdmd_2 into the optimum target seconddriving/braking force determiner 241 a_2.

Regarding the third wheel W3, the actuator operation target valuesynthesizer 24 directly inputs an FF target third wheel brakedriving/braking force of the actuator operation FF target value as an FFtotal target third wheel driving/braking force FFtotal_3 into an optimumtarget third driving/braking force determiner 241 a_3. Further, the sumof this FFtotal_3 and the FB target third wheel brake driving/brakingforce Fxfbdmd_3 of the actuator operation FB target value is determinedby an adder 245. Then, the sum is input as an unlimited target thirdwheel driving/braking force Fxdmd_3 into the optimum target thirddriving/braking force determiner 241 a_3.

Regarding the fourth wheel W4, the actuator operation target valuesynthesizer 24 directly inputs an FF target fourth wheel brakedriving/braking force of the actuator operation FF target value as an FFtotal target fourth wheel driving/braking force FFtotal_4 into anoptimum target fourth driving/braking force determiner 241 a_4. Further,the sum of this FFtotal_4 and the FB target fourth wheel brakedriving/braking force Fxfbdmd_4 of the actuator operation FB targetvalue is determined by an adder 246. Then, the sum is input as anunlimited target fourth wheel driving/braking force Fxdmd_4 into theoptimum target fourth driving/braking force determiner 241 a_4.

Here, to generalize the FF total target n-th wheel driving/braking forceFFtotal_n(n=1, 2, 3, 4), it means the total sum of a feedforward targetvalue of the driving/braking force of the n-th wheel Wn by an operationof the driving system of the driving/braking device 3A (FF target n-thwheel driving system driving/braking force) and a feedforward targetvalue of the driving/braking force of the n-th wheel Wn by an operationof the braking device (FF target n-th wheel brake driving/brakingforce). In this case, according to the embodiments in the presentdescription, the driving wheels of the actual vehicle 1 are the frontwheels W1 and W2, and the rear wheels W3 and W4 are the driven wheels;hence, for the rear wheels W3 and W4, the FF target n-th wheel brakedriving/braking force (n=3, 4) is directly determined as the FF totaltarget n-th wheel driving/braking force FFtotal_n.

Further, the unlimited target n-th wheel driving/braking forceFxdmd_n(n=1, 2, 3, 4) is the sum of the FF total target n-th wheeldriving/braking force FFtotal_n and the FB n-th wheel brakedriving/braking force, so that it means the total driving/braking forceof the n-th wheel required by a feedforward control operation of thedriving/braking device 3A (a feedforward control operation based on atleast a drive operation input) and a feedback control operation (afeedback control operation based on at least state amount errors γerrand βerr).

Then, the actuator operation target value synthesizer 24 determines thetarget n-th wheel driving/braking force Fxcmd_n, which is the finaltarget value of the driving/braking force of each n-th wheel Wn, by theoptimum target n-th driving/braking force determiner 241 a _(—) n (n=1,2, 3, 4), and also determines a target n-th wheel slip ratio, which isthe final target value of the slip ratio of the n-th wheel.

In this case, the optimum target n-th driving/braking force determiner241 a _(—) n (n=1, 2, 3, 4) receives a latest value (current time value)of the actual side slip angle of the n-th wheel Wn (more specifically,the actual front wheel side slip angle βf_act when n=1, 2 or the actualrear wheel side slip angle βr_act when n=3, 4) and a latest value(current time value) of the estimated friction coefficient μestm inaddition to FFtotal_n and Fxdmd_n. Although not shown, the optimumtarget n-th driving/braking force determiner 241 a _(—) n(n=1, 2)associated with the front wheels W1 and W2 also receives a latest value(current time value) of the actual front wheel steering angle δf_act.Then, the optimum target n-th driving/braking force determiner 241 a_(—) n(n=1, 2, 3, 4) determines the target n-th wheel driving/brakingforce Fxcmd_n and the target n-th wheel slip ratio on the basis of theinputs supplied thereto, respectively, as will be described later.

Further, the actuator operation target value synthesizer 24 inputs theactive steering FB target lateral force Fyfbdmd_f of the actuatoroperation FB target value and the FF target front wheel steering angleδf_ff of the actuator operation FF target value into an optimum targetactive steering angle determiner 247 so as to determine target frontwheel steering angles δfcmd, which are the final steering angle targetvalues of the front wheels W1 and W2 by the optimum target activesteering angle determiner 247. Incidentally, the δfcmd means the finaltarget values of the steering angles themselves (the steering anglesbased on the longitudinal direction of the actual vehicle 1) of thefront wheels W1 and W2 by an operation of an actuator if the steeringdevice 3B is the actuator-driven steering device. Meanwhile, if thesteering device 3B is the actuator-assisted steering device, then itmeans the final target values of the correction amounts of the steeringangles of the front wheels W1 and W2 by an operation of an actuator.

The actuator operation target value synthesizer 24 directly outputs theFF target n-th wheel driving system driving/braking force(n=1, 2) of theactuator operation FF target value without processing it as the targetn-th wheel driving system driving/braking force, which is the finaltarget value of the driving/braking force of the n-th wheel Wn by anoperation of the driving system of the driving/braking device 3A.Moreover, the actuator operation target value synthesizer 24 directlyoutputs the FF target transmission reduction gear ratio of the actuatoroperation FF target value without processing it as a target transmissionreduction gear ratio, which is the final target value of the reductiongear ratio (speed change ratio) of the speed change gear of thedriving/braking device 3A.

The processing by the optimum target n-th driving/braking forcedeterminer 241 a _(—) n(n=1, 2, 3, 4) will be explained below in detail.FIG. 19 is a flowchart showing the processing by the optimum target n-thdriving/braking force determiner 241 a _(—) n.

Referring to the figure, first, in S100, it is preconditioned that theside slip angle of the n-th wheel Wn (n=1, 2, 3, 4) is an actual sideslip angle (more specifically, the actual front wheel side slip angleβf_act for n=1, 2 and the actual rear wheel side slip angle βr_act forn=3, 4), and a road surface friction coefficient (the coefficient offriction between the n-th wheel Wn and a road surface) is the estimatedfriction coefficient μestm. Then, based on the precondition, an n-thwheel driving/braking force candidate Fxcand_n, which is the value ofthe driving/braking force of the n-th wheel Wn closest to the unlimitedtarget n-th wheel driving/braking force Fxdmd_n (including a case ofagreement therebetween), and an n-th wheel slip ratio candidate Scand_n,which is the value of the slip ratio of the n-th wheel Wn associatedtherewith, are determined.

In general, there is a constant correlation based on the characteristicsof wheel tires or the characteristics of a suspension device among theside slip angle and a road surface reaction force (a driving/brakingforce, a lateral force, and a ground contact load), a slip ratio and aroad surface friction coefficient of each wheel. For example, there is acorrelation indicated by expressions (2.57), (2.58), (2.72), and (2.73)in the aforesaid non-patent document 1 among a side slip angle, a roadsurface reaction force (a driving/braking force, a lateral force, and aground contact load), a slip ratio and a road surface frictioncoefficient of each wheel. Moreover, if, for example, the ground contactload and the road surface friction coefficient are set to be constant,then there is a correlation as shown in FIG. 2.36 of the aforesaidnon-patent document 1 among the side slip angle, the driving/brakingforce, the lateral force, and the slip ratio of each wheel. Hence, theroad surface reaction force and the slip ratio of each wheel when theside slip angle and the road surface friction coefficient individuallytake certain values cannot respectively take independent values;instead, the values thereof change according to the aforesaidcorrelations (hereinafter referred to as wheel characteristicsrelations). The slip ratio takes a negative value when thedriving/braking force is a driving/braking force in the drivingdirection (>0), while it takes a positive value when the driving/brakingforce is a driving/braking force in the braking direction (<0).

Thus, the processing in S100 in the present embodiment determines adriving/braking force that is closest to or agrees with the unlimitedtarget n-th wheel driving/braking force Fxdmd_n (a driving/braking forcethat provides a minimum absolute value of a difference from Fxdmd_n) anda slip ratio associated with the driving/braking force from the actualside slip angle βf_act or βr_act (latest value) of the n-th wheel Wn andthe estimated road surface friction coefficient μestm (latest value) onthe basis of a map which shows a relationship among a side slip angle, aroad surface friction coefficient, a driving/braking force, and a slipratio of the n-th wheel Wn and which has been prepared in advance. Then,the driving/braking force and the slip ratio determined as describedabove are determined as an n-th wheel driving/braking force candidateFxcand_n and an n-th wheel slip ratio candidate Scand_n.

For the map used for the processing, the aforesaid wheel characteristicsrelationship, for example, may be specified or estimated beforehand byvarious experiments or the like or on the basis of the tirecharacteristics of the wheels W1 to W4 or the characteristics of thesuspension device 3C, and the map may be prepared on the basis of thespecified or estimated wheel characteristics relationship. The groundcontact loads of n-th wheels Wn may be added as variable parameters tothe map. In this case, the actual ground contact load Fzact_n of then-th wheel Wn may be input to the optimum target n-th driving/brakingforce determiner 241 a _(—) n to determine Fxcand_n and Scand_n from theactual side slip angle βf_act or βr_act, the estimated frictioncoefficient μestm, and the actual ground contact load Fzact_n of then-th wheel Wn. However, fluctuations in the actual ground contact loadFzact_n are relatively small in general, so that the actual groundcontact load Fzact_n may be regarded as a constant value.

Supplementally, if Fxdmd_n exists in a range of values ofdriving/braking forces that can be generated (that can be applied from aroad surface) in the n-th wheel Wn (driving/braking forces that can begenerated on the basis of the aforesaid wheel characteristicsrelationship) corresponding to a set of the actual side slip angleβf_act or βr_act and the estimated road surface friction coefficientμestm of the n-th wheel Wn or a set of these and the actual groundcontact load Fzact_n, then the Fxdmd_n may be directly determined asFxcand_n without processing it. Further, if Fxdmd_n deviates from therange, then an upper limit value (>0) or a lower limit value (<0) of therange, whichever is closer to Fxdmd_n may be determined as Fxcand_n.

Further, corresponding to the set of the actual side slip angle βf_actor βr_act and the estimated road surface friction coefficient μestm ofthe n-th wheel Wn or the set of these and the actual ground contact loadFzact_n, a relationship between the slip ratio and the driving/brakingforce that can be generated in the n-th wheel Wn (a relationship betweenthe slip ratio and the driving/braking force that can be generatedaccording to the wheel characteristics relationship) will generally be arelationship in which the driving/braking forces have peak values(extremal values) with respect to changes in the slip ratio (a graphhaving slip ratio values on the axis of abscissas and thedriving/braking force magnitude values on the axis of ordinates will bea graph that bulges upward). For this reason, in some cases, there aretwo types of slip ratio values that correspond to the values ofdriving/braking forces whose absolute values are smaller than the peakvalues. If there are two types of slip ratio values corresponding toFxcand_n as described above, then, of the two types of slip ratiovalues, the slip ratio value that is closer to zero may be determined asan n-th wheel slip ratio candidate Scand_n. In other words, in therelationship between the slip ratio and the driving/braking force of then-th wheel Wn (the relationship based on the wheel characteristicsrelationship), the n-th wheel slip ratio candidate Scand_n may bedetermined within a range between the slip ratio value, at which thedriving/braking force reaches a peak value, and zero.

Supplementally, within the range between the slip ratio value, at whichthe driving/braking force reaches a peak value, and zero, the absolutevalue of a driving/braking force monotonously increases as the absolutevalue of the slip ratio increases from zero.

Subsequently, the procedure proceeds to S102 wherein an n-th wheeldriving/braking force at the generation of a maximum moment Fxmmax_n andan n-th wheel slip ratio at the generation of a maximum moment Smmax_n,which is a slip ratio corresponding to the above Fxmmax_n, aredetermined under the same precondition as that in S100. Here, the n-thwheel driving/braking force at the generation of a maximum momentFxmmax_n means the value of a driving/braking force component of a roadsurface reaction force that causes a moment in the yaw directiongenerated about the center-of-gravity point G of the actual vehicle 1 bya road surface reaction force to become maximum toward the same polarity(direction) as the polarity of the aforesaid feedback yaw moment basicrequired value Mfbdmd, the driving/braking force component being acomponent in a road surface reaction force that can be generated in then-th wheel Wn when the side slip angle of the n-th wheel Wn is theactual side slip angle βf_act or βr_act and the road surface frictioncoefficient is the estimated friction coefficient μestm (morespecifically, the resultant force of the driving/braking force and thelateral force that can be applied to the n-th wheel Wn from a roadsurface according to the wheel characteristics relationship). In thiscase, Fxmmax_n and Smmax_n are determined within a range wherein theabsolute value of the driving/braking force monotonously increases asthe absolute value of the slip ratio increases from zero in therelationship between the driving/braking force and the slip ratio of then-th wheel Wn (the relationship based on the wheel characteristicsrelationship). Thus, Smmax_n is determined to take a value between theslip ratio value, at which the driving/braking force reaches a peakvalue, and zero.

In S102, regarding the front wheels W1 and W2 (when n=1 or 2), the n-thwheel driving/braking force at the generation of a maximum momentFxmmax_n and the n-th wheel slip ratio at the generation of a maximummoment Smmax_n corresponding thereto are determined from, for example,the actual front wheel side slip angle βf_act, the estimated frictioncoefficient μestm, and the actual front wheel steering angle δf_actaccording to a map prepared beforehand (a map showing the relationshipamong front wheel side slip angles, road surface friction coefficients,front wheel steering angles, driving/braking forces at the generation ofmaximum moments, and slip ratios at the generation of maximum moments(the relationship based on the wheel characteristics relationship).Alternatively, from among the sets of driving/braking forces and lateralforces of the n-th wheel Wn (n=1 or 2) that can be generated withrespect to sets of βf_act and μestm, the set of a driving/braking forceand a lateral force that causes a moment in the yaw direction generatedby the resultant force thereof about the center-of-gravity point G ofthe actual vehicle 1 to reach its maximum level is explorativelydetermined on the basis of the map showing the relationship among thefront wheel side slip_angles, road surface friction coefficients, slipratios, driving/braking forces, and lateral forces, and the actual frontwheel steering angle δf_act. Then, the driving/braking force and theslip ratio associated with the set may be determined as Fxmmax_n andSmmax_n, respectively.

Further, regarding the rear wheels W3 and W4, (when n=3 or 4), the n-thwheel driving/braking force at the generation of a maximum momentFxmmax_n and the n-th wheel slip ratio at the generation of a maximummoment Smmax_n corresponding thereto are determined from, for example,the actual rear wheel slip angle βr_act and the estimated frictioncoefficient μestm according to a map prepared beforehand (a map showingthe relationship among rear wheel side slip angles, road surfacefriction coefficients, driving/braking forces at the generation ofmaximum moments, and slip ratios at the generation of maximum moments(the relationship based on the wheel characteristics relationship).Alternatively, from among the sets of driving/braking forces and lateralforces of the n-th wheel Wn (n=3 or 4) that can be generated withrespect to sets of βr_act and μestm, the set of a driving/braking forceand a lateral force that causes a moment in the yaw direction generatedby the resultant force thereof about the center-of-gravity point G ofthe actual vehicle 1 to reach a maximum level is explorativelydetermined according to the map showing the relationship among the rearwheel side slip angles, the road surface friction coefficients, the slipratios, the driving/braking forces, and the lateral forces. Then, thedriving/braking force and the slip ratio associated with the set may bedetermined as Fxmmax_n and Smmax_n, respectively.

Incidentally, the processing in S102 may include the actual groundcontact load Fzact_n of the n-th wheel Wn as a variable parameter aswith the case explained in relation to the processing in S100 describedabove.

Subsequently, the processing in S104 to S112 is carried out, as will bedescribed later, so as to determine the target n-th wheeldriving/braking force Fxcmd_n. In this case, the target n-th wheeldriving/braking force Fxcmd_n is determined to satisfy the followingconditions (1) to (3). Regarding conditions (1) to (3), the priorityrank is higher in the order of (1), (2), and (3). If no target n-thwheel driving/braking force Fcmd_n that satisfies all the conditions (1)to (3) can be determined, then the target n-th wheel driving/brakingforce Fxcmd_n is determined such that a condition with higher priorityis preferentially satisfied.

Condition (1): If an FF total target n-th wheel driving/braking forceFFtotal_n and a target n-th wheel driving/braking force Fxcmd_n aredriving/braking forces in the braking direction, then the magnitude (theabsolute value) of the target n-th wheel driving/braking force Fxcmd_nis not smaller than the magnitude (the absolute value) of the FF totaltarget n-th wheel driving/braking force FFtotal_n. In other words,0>Fxcmd_n>FFtotal_n does not happen.

Condition (2): If the target n-th wheel driving/braking force Fxcmd_nhas the same polarity as that of the n-th wheel driving/braking forceFxmmax_n at the generation of a maximum moment, then the magnitude (theabsolute value) of Fxcmd_n does not exceed the magnitude (the absolutevalue) of the Fxmmax_n. In other words, Fxcmd_n>Fxmmax_n>0 orFxcmd_n<Fxmmax_n<0 does not happen.

Condition (3): The target n-th wheel driving/braking force Fxcmd_nagrees with the n-th wheel driving/braking force candidate Fxcand_n asmuch as possible (more precisely, the absolute value of a differencebetween Fxcmd_n and Fxcand_n is minimized).

Condition (1) is a condition for preventing the target n-th wheeldriving/braking force Fxcmd_n from becoming smaller than thedriving/braking force in the braking direction of the n-th wheel Wn ofthe actual vehicle 1 (this corresponds to FFtotal_n) required by anoperation of the brake pedal performed by the driver of the actualvehicle 1. Supplementally, according to the embodiments in the presentdescription, the rear wheels W3 and W4 are driven wheels, so that the FFtotal target n-th wheel driving/braking force FFtotal_n(n=3, 4) and thetarget n-th wheel driving/braking force Fxcmd_n(n=3, 4) related to therear wheels W3 and W4 always take values of zero or less. Accordingly,regarding the rear wheels W3 and W4, condition (1) is equivalent to acondition that “the magnitude (the absolute value) of the target n-thwheel driving/braking force Fxcmd_n does not become smaller than themagnitude (the absolute value) of the FF total target n-th wheeldriving/braking force FFtotal_n.”

Further, condition (2) is a condition for preventing a lateral forcegenerated in the n-th wheel Wn on the basis of the target n-th wheeldriving/braking force Fxcmd_n from becoming excessively small.

Further, condition (3) is a condition for satisfying as much as possiblethe control requirements (targets) of operations of the actuator devices3 determined by the actuator operation FB target value determiner 20 band the FF law 22. Incidentally, Fxcand_n is, as described above, thevalue of a driving/braking force closest to the unlimited target n-thwheel driving/braking force Fxdmd_n (including a case of agreementtherebetween) within a range of the values of driving/braking forcesthat can be generated in the n-th wheel Wn according to the wheelcharacteristics relationship (a wheel characteristics relationshipobserved when it is preconditioned that the side slip angle of the n-thwheel Wn is an actual side slip angle βf_act or βr_act and a roadsurface friction coefficient is the estimated friction coefficientμestm). Therefore, the condition (3) is, in other words, equivalent to acondition that the target n-th wheel driving/braking force Fxcmd_n takesa value within the range of values of driving/braking forces that can begenerated in the n-th wheel Wn according to the wheel characteristicsrelationship (the wheel characteristics relationship observed when it ispreconditioned that the side slip angle of the n-th wheel Wn is theactual side slip angle βf_act or βr_act and a road surface frictioncoefficient is the estimated friction coefficient μestm) and agrees withor approximates (the absolute value of a difference from Fxdmd_n isminimized) the unlimited target n-th wheel driving/braking force Fxdmd_n(a driving/braking force based on a control requirement) as much aspossible.

To be more specific, the processing of S104 to S112 described above iscarried out as follows. First, the procedure proceeds to S104 wherein itis determined whether the magnitude relationship between Fxcand_ndetermined in S100 and Fxmmax_n determined in S102 is0>Fxmmax_n>Fxcand_n or 0<Fxmmax_n<Fxcand_n. If the result of thedetermination is NO, then the procedure proceeds to S106 wherein thevalue of Fxcand_n is substituted into the target n-th wheeldriving/braking force Fxcmd_n. More specifically, if Fxcand_n andFxmmax_n have polarities that are different from each other or if theFxcand_n and Fxmmax_n have the same polarity and the magnitude (theabsolute value) of Fxcand_n is the magnitude (the absolute value) ofFxmmax_n or less, then the value of Fxcand_n is directly substitutedinto Fxcmd_n. Incidentally, the value of Fxcand_n is substituted intoFxcmd_n (provided Fxcmd_n=0) also when Fxcand_n=0 (at this time, Fxdmd_nis also zero).

Meanwhile, if the determination result in S104 is YES, then theprocedure proceeds to S108 wherein the value of Fxmmax_n (the valuedetermined in S102) is substituted into the target n-th wheeldriving/braking force Fxcmd_n.

By the processing up to this point, Fxcmd_n is determined such that theconditions (2) and (3) are satisfied (provided that condition (2) isgiven a higher priority).

After the processing in S106 or S108, the procedure proceeds to S110wherein it is determined whether the magnitude relationship between theFF total target n-th wheel driving/braking force FFtotal_n and thecurrent target n-th wheel driving/braking force Fxcmd_n (the valuedetermined in S106 or S108) is 0>Fxcmd_n>FFtotal_n. If the result of thedetermination is YES, then the procedure proceeds to S112 whereinFFtotal_n is re-substituted into the target n-th wheel driving/brakingforce Fxcmd_n. More specifically, if the FF total target n-th wheeldriving/braking force FFtotal_n and the n-th wheel driving/braking forcecandidate Fxcmd_n determined in S106 or S108 are driving/braking forcesin the braking direction and the magnitude (the absolute value) ofFxcmd_n is smaller than the magnitude (the absolute value) of FFtotal_n,then the value of FFtotal_n is substituted into Fxcmd_n. If thedetermination result in S110 is NO, then the value of Fxcmd_n at thatinstant is maintained as it is.

By the aforesaid processing in S104 to S112, as previously described,basically, the target n-th wheel driving/braking force Fxcmd_n isdetermined such that the conditions (1) to (3) are satisfied. Further,if no target n-th wheel driving/braking force Fxcmd_n that satisfies allthe conditions (1) to (3) can be determined, then the target n-th wheeldriving/braking force Fxcmd_n is determined such that a condition havinga higher priority is preferentially satisfied.

If the determination result in S110 is YES, or after the processing inS112, the processing in S114 is carried out. In this S114, a slip ratioassociated with Fxcmd_n determined by the processing in S106 to S112 asdescribed above is determined as the target n-th wheel slip ratioScmd_n. In this case, by the processing in S104 to S112, Fxcmd_n takesthe value of one of Fxcand_n, Fxmmax_n, and FFtotal_n. And, ifFxcmd_n=Fxcand_n, then the n-th wheel slip ratio candidate Scand_ndetermined in S100 is determined as Scmd_n. If Fxcmd_n=Fxmmax_n, thenthe n-th wheel slip ratio at the generation of a maximum moment Smmax_ndetermined in S102 is determined as Scmd_n. If Fxcmd_n=FFtotal_n, thenthe slip ratio associated with FFtotal_n is determined according to, forexample, a map used for the processing in S100, and the determined slipratio may be determined as Scmd_n. In this case, if there are two typesof values of the slip ratio associated with FFtotal_n, then a slip ratiovalue that is closer to zero (a value within the range between a slipratio value, at which the driving/braking force of the n-th wheel Wnreaches a peak value, and zero) may be determined as Scmd_n. IfFFtotal_n deviates from the range of the values of driving/brakingforces that can be generated in the n-th wheel Wn in the map, then aslip ratio associated with the value of the driving/braking force thatis closest to FFtotal_n within the range may be determined as Scmd_n.

The above has explained in detail the processing by the optimum targetn-th driving/braking force determiner 241 a _(—) n (n=1, 2, 3, 4).

In the present embodiment, the target n-th wheel driving/braking forceFxcmd_n has been determined first and then the target n-th wheel slipratio Scmd_n associated therewith has been determined; reversely,however, the target n-th wheel slip ratio Scmd_n may be determined, andthen the target n-th wheel driving/braking force Fxcmd_n associatedtherewith may be determined. In this case, the target n-th wheel slipratio Scmd_n may be determined by the same processing as that in S104 toS112 described above on the basis of conditions related to the targetn-th wheel slip ratio Scmd_n associated with the aforesaid conditions(1) to (3). Then, after that, Fxcmd_n associated with the Scmd_n may bedetermined. In this case, in the relationship between the slip ratiosand the driving/braking forces based on the wheel characteristicsrelationship of the n-th wheel Wn, Scmd_n is determined within a rangebetween the slip ratio value, at which the driving/braking force reachesa peak value, and zero.

The processing by the optimum target active steering angle determiner247 will now be explained. FIG. 20 is a functional block diagram showingthe processing by the optimum target active steering angle determiner247.

Referring to the figure, the optimum target active steering angledeterminer 247 first determines, by a processor 247 a on the basis ofFyfbdmd_f, the FB active steering angle δf_fb, which indicates changeamounts of the steering angles of the front wheels W1 and W2 requiredfor the actual vehicle 1 to generate the active steering FB targetlateral force Fyfbdmd_f determined by the actuator operation FB targetvalue determiner 20 b in the front wheels W1 and W2 (more specifically,the resultant force of a lateral force of the front wheel W1 and alateral force of the front wheel W2 is changed by Fyfbdmd_f). In thiscase, the processor 247 a determines the cornering power Kf_1 of thefirst wheel W1 according to a predetermined function expression or a mapon the basis of, for example, the actual ground contact load Fzact_1 ofthe first wheel W1, and also determines the cornering power Kf_2 of thesecond wheel W2 according to a predetermined function expression or amap on the basis of the actual ground contact load Fzact_2 of the secondwheel W2. The function expression or map is set in advance on the basisof the tire characteristics of the front wheels W1 and W2 of the actualvehicle 1. Then, the cornering powers Kf_1 and Kf_2 are used todetermine the FB active steering angle δf_fb according to the followingexpression 30.

δf _(—) fb=(1/(Kf _(—)1+Kf _(—)2))·Fyfbdmd _(—) f   Expression 30

The FB active steering angle δf_fb determined as shown above correspondsto the correction amount of a front wheel side slip angle required tochange the resultant force of the lateral forces of the front wheels W1and W2 by Fyfbdmd_f.

Normally, changes in the actual ground contact loads Fzact_1 and Fzact_2are small, so that the coefficient (1/(Kf_1+Kf_2)) by which Fyfbdmd_f ismultiplied in expression 30 may be set to a constant value.

Subsequently, the optimum target active steering angle determiner 247adds the δf_fb determined as described above to the FF target frontwheel steering angle δf_ff by an adder 247 b so as to determine thetarget front wheel steering angle δfcmd.

If the active steering FB target lateral force Fyfbdmd_f based on thestate amount errors γerr and βerr is not determined or if Fyfbdmd_f=0 isalways maintained, then δf_ff may be directly determined as the targetfront wheel steering angle δf_cmd.

Up to this point, the processing by the actuator operation target valuesynthesizer 24 has been explained in detail.

[About the Actuator Drive Control Unit]

The actuator drive control unit 26 operates the actuator devices 3 ofthe actual vehicle 1 such that the target value determined by theactuator operation target value synthesizer 24 is satisfied. Forexample, the actuator manipulated variable of the driving system isdetermined such that the driving/braking force (the driving/brakingforce in the driving direction) of the first wheel W1 by an operation ofthe driving system of the driving/braking device 3A becomes the targetfirst wheel driving system driving/braking force, and the driving systemis operated on the basis thereof. Further, the actuator manipulatedvariable of the braking device is determined such that thedriving/braking force of the actual road surface reaction force of thefirst wheel W1 (the sum of the driving/braking force of the first wheelW1 by an operation of the driving system and the driving/braking forceof the first wheel W1 by an operation of the braking device (thedriving/braking force in the braking direction)) becomes the targetfirst wheel driving/braking force Fxcmd_1, and the braking device isactuated on the basis thereof. Further, in this case, the operation ofthe driving system or the braking device is adjusted so as to bring adifference between the actual slip ratio of the first wheel W1 and thetarget first wheel slip ratio Scmd_1 close to zero. The same applies tothe remaining wheels W2 to W4.

Further, if the steering device 3B is an actuator-driven steeringdevice, then the actuator manipulated variable of the steering device 3Bis determined such that the actual front wheel steering angle δf_actagrees with the target front wheel steering angle δfcmd, and theoperation of the steering device 3B is controlled on the basis thereof.If the steering device 3B is an actuator-assisted steering device, thenthe operation of the steering device 3B is controlled such that theactual front wheel steering angle δf_act agrees with the sum of thetarget front wheel steering angle δf_cmd and a mechanical steering anglecomponent based on the steering angle θh.

The reduction gear ratio of the speed change gear of the driving systemof the driving/braking device 3A is controlled on the basis of thetarget transmission reduction gear ratio.

Regarding the control amounts of the driving/braking forces of thewheels W1 to W4, lateral forces and the like, the operations of thedriving/braking device 3A, the steering device 3B, and the suspensiondevice 3C tend to interfere with each other. In such a case, theoperations of the driving/braking device 3A, the steering device 3B, andthe suspension device 3C are desirably controlled integrally by theprocessing of non-interference in order to control the control amountsto target values.

Second Embodiment

A second embodiment of the present invention will now be explained withreference to FIG. 21. The present embodiment differs from the firstembodiment described above only partly in processing, so that theexplanation will be focused mainly on different aspects and theexplanation of the same portions will be omitted. Further, in theexplanation of the present embodiment, the same constituent portions orthe same functional portions as those of the first embodiment will beassigned the same reference characters as those in the first embodiment.

According to a feedback control theory, basically, an actuator operationFB target value is ideally determined such that a feedback yaw momentbasic required value Mfbdmd based on the state amount errors γerr andβerr is satisfied. However, in the aforesaid first embodiment, a momentin the yaw direction generated about the center-of-gravity point G ofthe actual vehicle 1 by an actuator operation FB target value incurs anexcess or deficiency relative to Mfbdmd due to the processing by thedead-zone processor 221, the limiter 222 d _(—) n or the like. Inaddition, there are cases where the road surface reaction forcesgenerated in the wheels W1 to W4 of the actual vehicle 1 on the basis ofactuator operation FB target values incur an excess or deficiencyrelative to the actuator operation FB target values due to theinfluences of the nonlinearity (e.g., a limiter or a saturationcharacteristic) in the processing function sections (e.g., the actuatoroperation target value synthesizer 24) from actuator operation FB targetvalues to actuator operation target values. This sometimes causes theroad surface reaction forces generated in the wheels W1 to W4 of theactual vehicle 1 to develop an excess or deficiency relative to idealroad surface reaction forces for approximating the state amount errorsγerr and βerr to zero.

Meanwhile, regarding the influences on the difference between the stateamount of a motion of the actual vehicle 1 and the state amount of amotion of the model vehicle, applying an additional road surfacereaction force by feeding the difference back to the actuator device 3of the actual vehicle 1 (a road surface reaction force for approximatingthe difference to zero) to the actual vehicle 1 is equivalent toapplying an external force, which is obtained by multiplying theadditional road surface reaction force by (−1), to the model vehicle.

According to the present embodiment, therefore, a virtual external forceto be applied to the model vehicle is corrected on the basis of theexcess or deficiency of the road surface reaction force generated ineach of the wheels W1 to W4 of the actual vehicle 1 relative to theideal road surface reaction force, thereby compensating for the excessor deficiency.

An explanation will be given with reference to FIG. 21. In the presentembodiment, a virtual external force determiner 20 a of the FBdistribution law 20 is provided with a processor 215 in addition to thefunctions in the aforesaid first embodiment.

The processor 215 first inputs into a processor 215 a, the actuatoroperation FB target values (current time values) determined aspreviously described in an actuator operation FB target value determiner20 b. Then, the processor 215 a calculates the road surface reactionforce correction amounts, which are the correction amounts of the roadsurface reaction forces acting on the wheels W1 to W4 of the actualvehicle 1 on the basis of the actuator operation FB target values (thecorrection amounts from the road surface reaction forces produced on thebasis of the actuator operation FF target values). In this case, theroad surface reaction force correction amounts are determined asfollows.

The road surface reaction force (the driving/braking force and thelateral force) acting on the n-th wheel Wn is estimated on the basis ofthe target n-th wheel driving/braking force Fxcmd_n (n=1, 2, 3, 4) andthe target slip ratio Sxcmd_n (n=1, 2, 3, 4) determined by an actuatoroperation target value synthesizer 24 on the basis of the actuatoroperation FE target value (current time value) and the actuatoroperation FF target value (current time value). At this time, theestimated value of the driving/braking force of the n-th wheel Wn may bedenoted by Fxcmd_n, and the lateral force may be determined by using amap or the like based on, for example, the aforesaid wheelcharacteristics relationship. More specifically, the lateral force maybe determined by using, for example, S200 and S202, expression 40 or thelike, which will be discussed hereinafter. Further, the same processingas that by the actuator operation target value synthesizer 24 is carriedout with the actuator operation FB target value being set to zero,thereby determining the target driving/braking force and the target slipratio of each n-th wheel Wn (n=1, 2, 3, 4) observed when the actuatoroperation FE target value is set to zero, and based thereon, the roadsurface reaction force (the driving/braking force and lateral force)acting on the n-th wheel Wn is estimated. Then, the difference in theroad surface reaction force of the n-th wheel Wn is determined with theactuator operation FE target value being different as mentioned above,and the difference is determined as the road surface reaction forcecorrection amount for the n-th wheel Wn.

Subsequently, the road surface reaction force correction amountdetermined as described above is supplied to a processor 215 b. Then,the processor 215 b calculates a total moment Mfb (a moment in the yawdirection) generated about the center-of-gravity point G of the actualvehicle 1 due to the road surface reaction force correction amount (theresultant force of a driving/braking force component and a lateral forcecomponent of the road surface reaction force correction amount) of eachof the wheels W1 to W4. To be specific, a moment in the yaw directiongenerated about the center-of-gravity point G of the actual vehicle 1 bythe road surface reaction force correction amount of the n-th wheel Wnis determined on the basis of primarily the road surface reaction forcecorrection amount of each n-th wheel Wn (n=1, 2, 3, 4) and the actualfront wheel steering angle δf_act (the parameters that define thegeometric relationship between each of the wheels W1 to W4 and thecenter-of-gravity point of the actual vehicle 1). Then, the moments aresynthesized on all the wheels W1 to W4 thereby to determine Mfb.

Subsequently, the feedback yaw moment basic required value Mfbdmd(current time value) determined by a processor 220 of the actuatoroperation FB target value determiner 20 b is subtracted from the momentMfb by a subtracter 215 c to determine an actual vehicle yaw momenterror Mfb_err (=Mfb−Mfbdmd). Incidentally, this actual vehicle yawmoment error Mfb_err means the excess or deficiency of the moment in theyaw direction, which is generated in the actual vehicle 1 due to theactuator operation FB target value, from Mfbdmd.

Subsequently, the actual vehicle yaw moment error Mfb_err is multipliedby a predetermined gain Cfb by a multiplier 215 d to determine a virtualexternal force compensating moment Mvir_c. The gain Cfb takes a value of0<Cfb<1 (a positive value of 1 or less). The virtual external forcecompensating moment Mvir_c means a moment in the yaw direction thatshould be generated about a center-of-gravity point Gd of the modelvehicle to bring a state amount error between the actual vehicle 1 andthe model vehicle close to zero, the state amount error occurring due toan excess or deficiency of the moment in the yaw direction, which isgenerated in the actual vehicle 1 due to an actuator operation FB targetvalue, from Mfbdmd.

Subsequently, the virtual external force determined as described aboveby the γβ limiter 202 (the output of the subtracter 207) is defined assecond temporary values Mvir′ (=Mvirtmp−Mvir_over) and Fvir′(=Fvirtmp−Fvir_over), and the second temporary values Mvir′, Fvir′ andthe virtual external force compensating moment Mvir_c are added up by anadder 215 e. This determines the virtual external forces Mvir and Fvir(current time values). To be more specific, the sum of the secondtemporary values Mvir′ and Mvir_c is determined as Mvir, while thesecond temporary value Fvir′ is directly determined as Fvir withoutprocessing it.

The construction and processing other than those explained above are thesame as those in the aforesaid first embodiment.

According to the present embodiment, the influences of the nonlinearityfrom the state amount errors γerr and βerr to an actuator operationtarget value exerted on the behaviors of βerr and γerr are reduced,allowing the γerr and βerr to converge to zero while maintaining highlinearity. In other words, the total sum of the feedback gains forconverging the state amount errors γerr and βerr to zero approximates adifference between the gain matrix Kfbdmd in the expression 23 and thegain matrix Kfvir in expression 15 (Kfbdmd−Kfvir).

In other words, the relationship between the difference between theexternal force acting on the model vehicle when the virtual externalforces Mvir and Fvir obtained by correcting the second temporary valuesMvir′ and Fvir′ by the virtual external force compensating moment Mvir_care input to a reference dynamic characteristics model 16 (a moment inthe yaw direction) and an external force acting on the actual vehicle 1caused by the actuator operation FB target value (a moment Mfb in theyaw direction), and the state amount errors γerr and βerr will be arelationship having higher linearity than the relationship between thedifference between the external force acting on the model vehicle whenthe second temporary values Mvir′ and Fvir′ of a virtual external forceare directly input as the virtual external forces Mvir and Fvir into thereference dynamic characteristics model 16 (a moment in the yawdirection) and an external force acting on the actual vehicle 1 causedby the actuator operation FB target value (a moment Mfb in the yawdirection), and the state amount errors γerr and βerr.

Third Embodiment

A third embodiment of the present invention will now be explained withreference to FIG. 22 to FIG. 24. The present embodiment differs from theaforesaid first embodiment only partly in processing, so that theexplanation will be focused mainly on the different aspect, and theexplanation of the same portions will be omitted. In the explanation ofthe present embodiment, the same constituent portions or the samefunctional portions as those of the first embodiment will be assignedthe same reference characters as those of the first embodiment.

In the aforesaid first embodiment, as the actuator operation FB targetvalue for the driving/braking device 3A, the aforesaid FB target n-thwheel brake driving/braking force Fxfbdmd_n, which means a correctionrequired value (a correction required value for bringing the stateamount errors γerr and βerr close to zero) of the driving/braking forceto be applied to the n-th wheel Wn (n=1, 2, 3, 4) by an operation of thebraking device of the driving/braking device 3A, has been determined. Inplace of this, according to the present embodiment, an FB target n-thwheel brake moment Mfbdmd_n (n=1, 2, 3, 4) is determined as the actuatoroperation FB target value for the driving/braking device 3A. The FBtarget n-th wheel brake moment Mfbdmd_n means the correction requiredvalue (the correction required value for bringing the state amounterrors γerr and βerr close to zero) of a moment in the yaw directiongenerated about a center-of-gravity point G of the actual vehicle 1 by aroad surface reaction force (more specifically, the resultant force of adriving/braking force and a lateral force) to be applied to the wheelsW1 to W4 by operating the braking device of the driving/braking device3A. Further, according to the present embodiment, the FB target n-thwheel brake moment Mfbdmd_n is used to determine an actuator operationtarget value.

Thus, the present embodiment differs from the aforesaid first embodimentin the processing by an actuator operation FB target value determiner 20b of the FB distribution law 20 and the processing by an actuatoroperation target value synthesizer 24. And, the constructions andprocessing other than these are the same as those of the firstembodiment.

The following will explain the processing by the actuator operation FBtarget value determiner 20 b and the processing by the actuatoroperation target value synthesizer 24 in the present embodiment.

FIG. 22 is a functional block diagram showing the processing function ofthe actuator operation FB target value determiner 20 b in the presentembodiment. Referring to the figure, the actuator operation FB targetvalue determiner 20 b first carries out the same processing as that inthe first embodiment by processors 220 and 221 to determine theaforesaid feedback yaw moment basic required value Mfbdmd and adead-zone excess feedback yaw moment required value Mfbdmd_a,respectively.

Subsequently, the actuator operation FB target value determiner 20 bcarries out the processing by an actuator operation FB target valuedistribution processor 222 to determine an actuator operation FB targetvalue. In this case, according to the present embodiment, each FB targetn-th wheel brake moment Mfbdmd_n (n=1, 2, 3, 4) is determined throughthe intermediary of processors 222 f _(—) n and 222 g _(—) n. Further,an active steering FB target lateral force Fyfbdmd_f is determined by aprocessor 222 e. The processing by the processor 222 e is the same asthat in the aforesaid first embodiment. Incidentally, the processor 222e may be omitted.

Each FB target n-th wheel brake moment Mfbdmd_n (n=1, 2, 3, 4) isdetermined as follows. Basically, the FB target n-th wheel brake momentMfbdmd_n (n=1, 2, 3, 4) is determined such that, if Mfbdmd_a ispositive, then the moment is generated by manipulating (correcting) theroad surface reaction forces of the left wheels W1 and W3 of the actualvehicle 1, and if Mfbdmd_a is negative, then the moment is generated bymanipulating (correcting) the road surface reaction forces of the rightwheels W2 and W4 of the actual vehicle 1.

To be more specific, first, each n-th wheel distribution gain Kn isdetermined by the processor 222 f _(—) n (n=1, 2, 3, 4) associated withthe wheels W1 to W4. The n-th wheel distribution gain Kn is determinedin the same manner as that in the first embodiment. More specifically,K1 and K2 associated with the front wheels W1 and W2 are respectivelydetermined as shown by, for example, the graph in the aforesaid FIG. 14(a) on the basis of the actual front wheel side slip angle βf_act as thefront wheel gain adjustment parameter. Further, K3 and K4 associatedwith the rear wheels W3 and W4 are respectively determined as shown by,for example, the graph of the aforesaid FIG. 14( b) on the basis of theactual rear wheel side slip angle βr_act as the rear wheel gainadjustment parameter. Then, each processor 222 f _(—) n (n=1, 2, 3, 4)multiplies Mfbdmd_a by the n-th wheel distribution gain Kn thereby todetermine an n-th wheel distribution moment basic value Mfb_n. Thepolarity (direction) of Mfb_n thus determined is the same as Mfbdmd_a.The n-th wheel distribution gain Kn may be determined in any one mannerexplained in the aforesaid first embodiment, besides it is determined asdescribed above on the basis of βf_act or βr_act. And, in this case, thefront wheel gain adjustment parameter and the rear wheel gain adjustmentparameter may use parameters other than βf_act or βr_act, as with theaforesaid first embodiment.

Subsequently, the actuator operation FB target value distributionprocessor 222 passes each of the n-th wheel distribution moment basicvalues Mfb_n (n=1, 2, 3, 4), which has been determined as describedabove, through a limiter 222 g _(—) n associated with the n-th wheel Wnto determine each of the FB target n-th wheel brake moments Mfbdmd_n.

Here, the graphs of the limiters 222 g _(—) n (n=1, 2, 3, 4) in FIG. 22are graphs showing the relationships between Mfb_n and Mfbdmd_n, thevalues in the direction of the axis of abscissas related to the graphsbeing the values of Mfb_n, while the values in the direction of the axisof ordinates being the values of Mfbdmd_n.

Among the limiters 222 g _(—) n, the limiters 222 g_1 and 222 g_3associated with the first wheel W1 and the third wheel W3 directlyoutput Mfb_n as Mfbdmd_n without processing it only if the values ofMfb_n (n=1, 3) supplied thereto are zero or positive values. If Mfb_n isa negative value, then the value of Mfbdmd_n to be output is set to zeroregardless of the value of Mfb_n. In other words, Mfbdmd_n is determinedby placing a restriction on Mfb_n by setting zero as the lower limitvalue.

Meanwhile, the limiters 222 g_2 and 222 g_4 associated with the secondwheel W1 and the fourth wheel W3 directly output Mfb_n as Mfbdmd_nwithout processing it only if the values of Mfb_n (n=2, 4) suppliedthereto are zero or negative values. If Mfb_n is a positive value, thenthe value of Mfbdmd_n to be output is set to zero regardless of thevalue of Mfb_n. In other words, Mfbdmd_n is determined by placing arestriction on Mfb_n by setting zero as the upper limit value.

By determining the FB target n-th wheel brake moment Mfbdmd_n (n=1, 2,3, 4) as described above, if Mfbdmd_a>0, then the road surface reactionforces of the left wheels W1 and W3 of the actual vehicle 1 arecorrected thereby to determine Mfbdmd_n such that a moment in the yawdirection that is substantially equal to Mfbdmd_a is generated about thecenter-of-gravity point G of the actual vehicle 1. In this case,Mfbdmd_1 and Mfbdmd_3 of the first wheel W1 and the third wheel W3,respectively, will be proportional to Mfbdmd_a (a value obtained bymultiplying Mfbdmd_a by K1 or K3). As a result, the relationship betweenchanges in Mfbdmd_a and changes in Mfbdmd_1 and Mfbdmd_3 will be aproportional relation. Further, the first wheel distribution gain K1 asthe front wheel gain and the third wheel distribution gain K3 as a rearwheel gain in the proportional relationship will change on the basis ofa front wheel gain adjustment parameter (βf_act in the presentembodiment) and a rear wheel gain adjustment parameter (βr_act in thepresent embodiment), respectively.

If Mfbdmd_a<0, then Mfbdmd_n is determined such that a moment in the yawdirection that is substantially equal to Mfbdmd_a is generated about thecenter-of-gravity point G of the actual vehicle 1 by correcting the roadsurface reaction forces of the right wheels W2 and W4 of the actualvehicle 1 by an operation of the braking device 3A of thedriving/braking device 3A. In this case, Mfbdmd_2 and Mfbdmd_4 of thesecond wheel W2 and the fourth wheel W4, respectively, will beproportional to Mfbdmd_a (a value obtained by multiplying Mfbdmd_a by K2or K4). As a result, the relationship between changes in Mfbdmd_a andchanges in Mfbdmd_2 and Mfbdmd_4 will be a proportional relation.Further, the second wheel distribution gain K2 as the front wheel gainand the fourth wheel distribution gain K4 as a rear wheel gain in theproportional relation will change on the basis of a front wheel gainadjustment parameter (βf_act in the present embodiment) and a rear wheelgain adjustment parameter (βr_act in the present embodiment),respectively.

The limiters 222 g _(—) n (n=1, 3) associated with the first wheel W1and the third wheel W3 may determine Mfbdmd_n by placing a restrictionon Mfb_n by setting a value that is slightly smaller than zero as thelower limit value of Mfbdmd_n. Similarly, the limiters 222 g _(—) n(n=2, 4) associated with the second wheel W2 and the fourth wheel W4 maydetermine Mfbdmd_n by placing a restriction on Mfb_n by setting a valuethat is slightly larger than zero as the upper limit value of Mfbdmd_n.

The above has explained in detail the processing by the actuatoroperation FB target value determiner 20 b in the present embodiment.

The processing by the actuator operation target value synthesizer 24 inthe present embodiment will now be explained with reference to FIG. 23and FIG. 24. FIG. 23 is a functional block diagram showing theprocessing function of the actuator operation target value synthesizer24, and FIG. 24 is a flowchart illustrating the processing by an optimumtarget n-th driving/braking force determiner of the processing function.

Referring to FIG. 23, the actuator operation target value synthesizer 24in the present embodiment is equipped with an optimum target n-thdriving/braking force determiner 241 b _(—) n (n=1, 2, 3, 4) whichdetermines a target n-th wheel driving/braking force Fxcmd_n and atarget n-th wheel slip ratio Scmd_n and an optimum active steering angledeterminer 247 which determines a target front wheel steering angleδfcmd.

The processing by the optimum active steering angle determiner 247 isthe same as that in the first embodiment. Meanwhile, the processing bythe optimum target n-th driving/braking force determiner 241 b _(—) ndiffers from that in the first embodiment. Further, as with theaforesaid first embodiment, the actuator operation target valuesynthesizer 24 outputs an FF target first wheel driving systemdriving/braking force, an FF target second wheel driving systemdriving/braking force, and an FF target transmission reduction gearratio of the actuator operation FF target value determined by theaforesaid FF law 22 as a target first wheel driving systemdriving/braking force, a target second wheel driving systemdriving/braking force, and a target transmission reduction gear ratio,respectively.

In the present embodiment, each of the optimum target n-thdriving/braking force determiners 241 b _(—) n (n=1, 2) associated withthe front wheels W1 and W2 receives an FF total target n-th wheeldriving/braking force FFtotal_n, which is the sum of an FF target n-thwheel brake driving/braking force and an FF target n-th wheel drivingsystem driving/braking force (this is determined by an adder 240, aswith the first embodiment) of the actuator operation FF target valuedetermined by the FF law 22, and an FB target n-th wheel brake momentMfbdmd_n of the actuator operation FB target value determined by theactuator operation FB target value determiner 20 b. The optimum targetn-th driving/braking force determiners 241 b _(—) n (n=1, 2) associatedwith the front wheels W1 and W2 receive a latest value (a current timevalue) of the actual front wheel side slip angle βf_act and a latestvalue (a current time value) of an estimated friction coefficient μestm,as with the first embodiment. In addition, although not shown, a latestvalue (a current time value) of the actual front wheel steering angleδf_act is also input to the optimum target n-th driving/braking forcedeterminer 241 b _(—) n (n=1, 2).

Further, each of the optimum target n-th driving/braking forcedeterminers 241 b _(—) n (n=3, 4) associated with the rear wheels W3 andW4 receives an FF target n-th wheel brake driving/braking force of theactuator operation FF target value determined by the FF law 22 as the FFtotal target n-th wheel driving/braking force FFtotal_n and alsoreceives an FB target n-th wheel brake moment Mfbdmd_n of the actuatoroperation FB target value determined by the actuator operation FB targetvalue determiner 20 b. Each of the optimum target n-th driving/brakingforce determiners 241 b _(—) n (n=3, 4) associated with the rear wheelsW3 and W4 also receives a latest value (a current time value) of theactual rear wheel side slip angle βr_act and a latest value (a currenttime value) of an estimated friction coefficient μestm, as with the caseof the first embodiment.

Then, each of the optimum target n-th driving/braking force determiners241 b _(—) n (n=1, 2, 3, 4) determines the target n-th wheeldriving/braking force Fxcmd_n and the target n-th wheel slip ratioScmd_n on the basis of the supplied inputs, and outputs the determinedresults.

The following will explain the processing by each of the optimum targetn-th driving/braking force determiners 241 b _(—) n (n=1, 2, 3, 4) withreference to FIG. 24.

First, in S200, it is preconditioned that the side slip angle of then-th wheel Wn (n=1, 2, 3, 4) is an actual side slip angle (morespecifically, the actual front wheel side slip angle βf_act if n=1 or 2and the actual rear wheel side slip angle βr_act if n=3 or 4), and aroad surface friction coefficient (the coefficient of friction betweenthe n-th wheel Wn and a road surface) is the estimated frictioncoefficient μestm. Then, based on the precondition, a slip ratio Sff_nassociated with the FF total target n-th wheel driving/braking forceFFtotal_n is determined. More specifically, based on the precondition,the value of the slip ratio associated with a driving/braking force thatagrees with or is closest to FFtotal_n in the driving/braking force thatcan be generated in the n-th wheel Wn is determined as Sff_n. In thiscase, the slip ratio associated with FFtotal_n may be determined on thebasis of, for example, the map used for the processing in S100 of FIG.19 in the aforesaid first embodiment, and the determined slip ratio maybe determined as Sff_n. If a slip ratio associated with FFtotal_n hastwo different values, then the slip ratio that is closer to zero isdetermined as Sff_n. In other words, in the relationship between theslip ratio of the n-th wheel Wn and the driving/braking force (therelationship based on the aforesaid wheel characteristics relationship),Sff_n is determined within the range between the value of the slipratio, at which the driving/braking force reaches a peak value (extremalvalue), and zero. If FFtotal_n deviates from the range of values of thedriving/braking forces that can be generated in the n-th wheel Wn underthe aforesaid precondition, then the value of the slip ratio associatedwith the value of a driving/braking force closest to FFtotal_n isdetermined as Sff_n.

Subsequently, the procedure proceeds to S202 wherein a lateral forceFyff_n of the n-th wheel Wn when the slip ratio of the n-th wheel Wn isSff_n is determined. In this case, the lateral force Fyff_n may bedetermined from the value of the actual side slip angle βf_act or βr_actof the n-th wheel Wn, the value of the estimated road surface frictioncoefficient μestm, and the value of Sff_n on the basis of, for example,a map which is prepared in advance and which shows the relationshipamong the side slip angle, the road surface friction coefficient, theslip ratio, and the lateral force of the n-th wheel Wn (the relationshipbased on the aforesaid wheel characteristics relationship).Incidentally, the map may include an actual ground contact load Fzact_nof the n-th wheel Wn as a variable parameter.

Subsequently, the procedure proceeds to S204 wherein a moment Mff_n inthe yaw direction that is generated about the center-of-gravity point Gof the actual vehicle 1 due to the resultant vector of FFtotal_n, whichis the driving/braking force of the n-th wheel Wn, and Fyff_n, which isthe lateral force of the n-th wheel Wn, when the slip ratio is Sff_n isdetermined. To be more specific, if the n-th wheel Wn is the front wheelW1 or W2 (n=1 or 2), then a position vector (a position vector on ahorizontal plane) of the center-of-gravity point G of the actual vehicle1 observed from the n-th wheel Wn is determined on the basis of theactual front wheel steering angle δf_act. Then, the outer product(vector product) of the position vector and the aforesaid resultantvector may be calculated so as to determine Mff_n. Further, if the n-thwheel Wn is the rear wheel W3 or W4 (n=3 or 4), then the outer product(vector product) of the position vector (a position vector on ahorizontal plane, which is set in advance) of the center-of-gravitypoint G of the actual vehicle 1 observed from the n-th wheel Wn and theaforesaid resultant force vector may be calculated so as to determineMff_n. The Mff_n may alternatively be determined according to a map,which is prepared beforehand, from FFtotal_n, Fyff_n and the actualfront wheel steering angle δf_act (if n=1 or 2) or from FFtotal_n andFyff_n (if n=3 or 4). The Mff_n thus determined corresponds to thefeedforward required moment (a required moment when Mfbdmd_n=0) of then-th wheel.

Subsequently, the procedure proceeds to S206 wherein the Mff_ndetermined as described above and the FB target brake moment Mfbdmd_nare added up thereby to calculate a temporary target moment candidateMcand_n, which is a temporary target value of a moment (a moment in theyaw direction) about the center-of-gravity point G of the actual vehicle1 by a road surface reaction force of the n-th wheel Wn. This Mcand_nmeans a moment in the yaw direction which should be generated about thecenter-of-gravity point G of the actual vehicle 1 on the basis of acontrol request in the n-th wheel Wn.

Subsequently, the procedure proceeds to S208 wherein an n-th wheel slipratio at the generation of a maximum moment Smmax_n is determined on aprecondition that the side slip angle of the n-th wheel Wn (n=1, 2, 3,4) is an actual side slip angle (more specifically, the actual frontwheel side slip angle βf_act if n=1 or 2 and the actual rear wheel sideslip angle βr_act if n=3 or 4), and a road surface friction coefficient(the coefficient of friction between the n-th wheel Wn and a roadsurface) is the estimated friction coefficient μestm. This processing iscarried out in the same manner as that for determining the n-th wheelslip ratio at the generation of a maximum moment Smmax_n in S102 of FIG.19 in the aforesaid first embodiment. However, Smmax_n is determinedsuch that the moment (maximum moment) generated about thecenter-of-gravity point G of the actual vehicle 1 by the resultant forceof the driving/braking force and the lateral force produced in the n-thwheel Wn in response thereto reaches a maximum value thereof toward thepolarity (direction) of the feedback yaw moment basic required valueMfbdmd.

Subsequently, the procedure proceeds to S210 wherein the slip ratioScand_n when a moment in the yaw direction agrees with the Mcand_n orbecomes closest to Mcand_n determined in S206 between the value ofSmmax_n determined as described above and zero is determined.Determining Scand_n as described above is equivalent to determining theslip ratio associated with a driving/braking force that satisfies theaforesaid conditions (2) and (3) (more specifically, satisfies condition(3) within a range in which condition (2) is satisfied).

The processing in S210 may exploratively determine Scand_n on the basisof, for example, the map which is prepared in advance and which showsthe relationship among the actual side slip angle, the road surfacefriction coefficient, the slip ratio, the driving/braking force, and thelateral force of the n-th wheel Wn (the relationship based on the wheelcharacteristics relationship) and the actual front wheel steering angleδf_act (if n=1 or 2), or according to the map (if n=3 or 4) under theaforesaid precondition.

Subsequently, the target n-th wheel slip ratio Scmd_n is determined bythe processing in S212 to S216. In this case, Scmd_n is determined suchthat the absolute value of the driving/braking force (thedriving/braking force in the braking direction) associated with Scmd_ndoes not become smaller than the absolute value of the FF total targetn-th wheel driving/braking force FFtotal_n if both Scand_n and Sff_n arepositive values (in other words, if the driving/braking forces of then-th wheels Wn associated with Scand_n and Sff_n, respectively, are boththe driving/braking forces in the braking direction).

To be more specific, it is determined in S212 whether Scand_n>Sff_n>0applies, and if the determination result is YES, then the procedureproceeds to S214 wherein the value of Scand_n is substituted intoScmd_n. If the determination result in S212 is NO, then the procedureproceeds to S216 wherein the value of Sff_n is substituted into Scmd_n.

Subsequently, the procedure proceeds to S218 wherein the driving/brakingforce of the n-th wheel Wn associated with the Scmd_n determined asdescribed above is determined as a target n-th wheel driving/brakingforce Fxcmd_n. In this case, Fxcmd_n associated with the value of theScmd_n is determined on the basis of, for example, a map which shows therelationship between slip ratios and driving/braking forces and which isprepared beforehand.

The above has described the processing by the optimum target n-thdriving/braking force determiner 242 b _(—) n in the present embodiment.

Supplementally, the present embodiment uses, in place of the condition(3) in the aforesaid first embodiment, a condition that the target n-thwheel driving/braking force Fxcmd_n takes a value within the range ofvalues of driving/braking forces that can be generated in the n-th wheelWn according to the aforesaid wheel characteristics relationship (thewheel characteristics relationship that holds on the basis of aprecondition that the side slip angle of the n-th wheel Wn is the actualside slip angle βf_act or βr_act and the road surface frictioncoefficient is the estimated friction coefficient μestm) and a moment inthe yaw direction generated about the center-of-gravity point G of theactual vehicle 1 by a road surface reaction force that has adriving/braking force component equal to Fxcmd_n among the road surfacereaction forces that can be generated in the n-th wheel Wn according tothe wheel characteristics relationship agrees with or is close to theaforesaid Mcand_n as much as possible (the absolute value of adifference from Mcand_n is minimized). In addition, among this condition(hereinafter referred to as condition (3)′) and the aforesaid conditions(1) and (2), the aforesaid condition (1) is defined as thehighest-priority condition and the condition (2) is defined as thenext-rank condition, and then the target n-th wheel driving/brakingforce Fxcmd_n is determined such that the conditions (1), (2), and (3)′are satisfied according to the order of priority. In this case, Fxcmd_nis determined by the processing up to S210 described above such thatcondition (3)′ is satisfied as much as possible within a range in whichcondition (2) is eventually satisfied. More specifically, if thedriving/braking force associated with Scand_n determined by theprocessing in S210 (the driving/braking force associated with Scmd_nobtained when the determination result in S212 is YES) is determined asthe target n-th wheel driving/braking force Fxcmd_n, then the Fxcmd_nwill satisfy conditions (2) and (3)′ while condition (2) being treatedas the preferential condition. Further, Fxcmd_n is determined such thatthe highest-priority condition (1) is satisfied by carrying out theprocessing in S212 to S216.

Fourth Embodiment

A fourth embodiment of the present invention will now be explained withreference to FIG. 25 and FIG. 26. The present embodiment differs fromthe aforesaid first embodiment only partly in processing, so that theexplanation will be focused mainly on the different aspect, and theexplanation of the same portions will be omitted. In the explanation ofthe present embodiment, the same constituent portions or the samefunctional portions as those of the first embodiment will be assignedthe same reference characters as those of the first embodiment.

The present embodiment differs from the first embodiment only in theprocessing by the optimum target n-th driving/braking force determiner241 a _(—) n (n=1, 2, 3, 4) of the actuator operation target valuesynthesizer 24 shown in FIG. 18 described above. In this case, accordingto the present embodiment, although not shown, each optimum target n-thdriving/braking force determiner 241 a _(—) n receives an estimatedfriction coefficient μestm and an actual road surface reaction force ofthe n-th wheel Wn (an actual driving/braking force Fxact_n, an actuallateral force Fyact_n, and an actual ground contact load Fzact_n) inaddition to the FF total n-th wheel driving/braking force FFtotal_n andthe unlimited n-th wheel driving/braking force Fxdmd_n. Then, eachoptimum target n-th driving/braking force determiner 241 a _(—) npresumes the relationship between the driving/braking force and thelateral force of the n-th wheel Wn on the basis of the estimatedfriction coefficient μestm and the actual road surface reaction force ofthe n-th wheel Wn, which have been input thereto. Further, by using theestimated relationship, a target n-th wheel driving/braking forceFxcmd_n and a target n-th wheel slip ratio Scmd_n are determined.

Here, as indicated by expression (2.42) in the aforesaid non-patentdocument 1, if the actual side slip angle of each n-th wheel Wn (n=1, 2,3, 4) takes a certain value, the relationship between a lateral forceFy_n and a driving/braking force Fx_n applied from a road surface to then-th wheel Wn can be generally approximated by an elliptical expressionshown below.

$\begin{matrix}\lbrack {{Mathematical}\mspace{14mu} {expression}{\mspace{11mu} \;}9} \rbrack & \; \\{{( \frac{Fx\_ n}{\mu \cdot {Fz\_ n}} )^{2} + ( \frac{Fy\_ n}{{Fy}\; 0{\_ n}} )^{2}} = 1} & {{Expression}\mspace{14mu} 40}\end{matrix}$

In expression 40, μ denotes a road surface friction coefficient, Fz_ndenotes a ground contact load of an n-th wheel Wn, and Fy0 _(—) ndenotes a lateral force when the driving/braking force Fx_n of the n-thwheel Wn is zero. Fy0 _(—) n generally changes with the side slip angleof the n-th wheel Wn. The polarity of Fy0 _(—) n is opposite from thepolarity of the actual slip angle of the n-th wheel Wn.

In the present embodiment, this expression 40 is the expression fordefining the relationship between a driving/braking force and a lateralforce of the n-th wheel Wn, and this expression 40 is used to determineFxcmd_n and Scmd_n. In this case, a value of an actual road surfacereaction force is used to specify Fy0 _(—) n of expression 40.

Referring to FIG. 25, the following will explain the processing by theoptimum target n-th driving/braking force determiner 241 a _(—) n (n=1,2, 3, 4) in the present embodiment. FIG. 25 is a flowchart showing theprocessing.

First, in S300, the value of Fy0 _(—) n of the above expression 40 (thevalue of the lateral force when the driving/braking force is zero) isdetermined on the basis of the actual road surface reaction forcesFxact_n, Fyact_n, and Fzact_n of the n-th wheel Wn (the latest values ofdetected values or estimated values) and the estimated frictioncoefficient μestm (latest value). More specifically, the values ofFxact_n, Fyact_n, Fzact_n, and μestm are substituted into Fx_n, Fy_n,Fz_n, and μ, respectively, of expression 40. Then, a solution iseffected on Fy0 _(—) n (in other words, by the expression shown in thefigure) to determine the value of Fy0 _(—) n. Incidentally, sqrt (A) inthe figure (A denoting a general variable) is a function for determiningthe square root of A. The polarity (sign) of Fy0 _(—) n is the same asthat of Fyact_n.

Subsequently, the procedure proceeds to S302 wherein the driving/brakingforce Fx_n that is closest to (including the case of agreement with) theaforesaid unlimited n-th wheel driving/braking force Fxdmd_n isdetermined, using the expression 40 (expression 40 with the value of Fy0_(—) n being the value determined in S300) as a restrictive condition(the restrictive condition defining the relationship between Fx_n andFy_n), and the determined Fx_n is defined as the n-th wheeldriving/braking force candidate Fxcand_n. In this case, the range ofvalues that the driving/braking force Fx_n may take under therestrictive condition of expression 40 is a range between −μ·Fzact_n andμ·Fzact_n. Incidentally, μ·Fzact_n means a maximum frictional forcebetween the n-th wheel Wn and a road surface. Hence, if the value ofFxdmd_n is a value within the range [−μ·Fzact_n, μ·Fzact_n], thenFxdmd_n is directly determined as Fxcand_n, and if the value of Fxdmd_ndeviates from the range [−μ·Fzact_n, μ·Fzact_n], then the value ofeither −μ·Fzact_n or μ·Fzact_n, whichever is closer to Fxcmd_n, isdetermined as Fxcand_n.

Subsequently, the procedure proceeds to S304 wherein a value of thedriving/braking force Fx_n at which the moment in the yaw directiongenerated about the center-of-gravity point G of the actual vehicle 1 bya road surface reaction force of the n-th wheel (the resultant force ofthe driving/braking force Fx_n and the lateral force Fy_n) reaches amaximum level is determined, using the expression 40 (expression 40 whenthe value of Fy0 _(—) n is the value determined in S300) as therestrictive condition, and the determined value is defined as the n-thwheel driving/braking force at the generation of a maximum momentFxmmax_n. More specifically, of the pairs of Fx_n and Fy_n conforming tothe relationship of the expression 40, the pair of Fx_n and Fy_n atwhich the moment in the yaw direction generated about thecenter-of-gravity point G of the actual vehicle 1 by the resultant forceof the pair of Fx_n and Fy_n reaches the maximum level is determined,and the value of Fx_n of the pair is determined as Fxmmax_n. The maximummoment here is a moment that reaches its maximum level toward the samepolarity as that of the feedback yaw moment basic required value Mfbdmd.The polarity of a lateral force associated with Fxcand_n is the same asthe polarity of Fy0 _(—) n (=the polarity of Fyact_n) determined inS300.

In this case, Fxmmax_n (Fxmmax_n when n=1 or 2) associated with thefront wheels W1 and W2 is calculated from the estimated frictioncoefficient μestm (latest value), the actual ground contact load Fzact_nof the n-th wheel Wn and the actual front wheel steering angle δf_act.Further, Fxmmax_n (Fxmmax_n when n=3 or 4) associated with the rearwheels W3 and W4 is calculated from the estimated friction coefficientμestm (latest value) and the actual ground contact load Fzact_n of then-th wheel Wn.

A method for calculating Fxmmax_1 related to the first wheel W1 will nowbe representatively explained with reference to FIG. 26. This FIG. 26schematically shows the actual vehicle 1 in a plan view, an ellipse C1in the figure showing the ellipse indicated by the expression 40. Apoint on the ellipse C1 associated with the pair of Fx_1 and Fy_1 thatcauses the moment generated about the center-of-gravity point G of theactual vehicle 1 to reach the maximum level is a point of contact Psbetween a straight line um in contact with the ellipse C1 and theellipse C1 on the straight line in parallel to a straight line u0connecting the central point of the first wheel W1 and thecenter-of-gravity point G of the actual vehicle 1 on a horizontal plane.In this example, it is assumed that Fxcand_1 takes a negative (in thebraking direction) driving/braking force, and Fx_1 at the point ofcontact Ps also takes a negative value.

Here, if an angle formed by the straight line um (or u0) with respect tothe longitudinal direction of the first wheel W1 is denoted by θ asshown in the figure, then a change rate of Fy_1 relative to Fx_1,∂Fy_1/∂Fx_1, at the point of contact Ps is equal to tan θ as indicatedby expression 41 given below. Further, tan θ is determined from theactual front wheel steering angle δf_act by the geometric computation ofexpression 42 given below.

∂Fy _(—)1/∂Fx _(—)1=tan θ  Expression 41

tan θ=(−Lf·sin δf_act+(df/2)·cos δf_act)/(Lf·cos δf_act+(df/2)·sinδf_act)   Expression 42

The meanings of df and Lf of expression 42 are the same as those in FIG.13 mentioned above.

Meanwhile, expression 43 given below is derived from the expression 40.

∂Fy _(—)1/∂Fx _(—)1=−(Fy0_(—)1/(μestm·Fzact_(—)1))²·(Fx _(—)1/Fy _(—)1)  Expression 43

From the expressions 41 and 43 and the expression 40, the value of Fx_1at the point of contact Ps, i.e., Fxmmax_1, is given by expression 44given below.

Fxmmax_(—)1=μestm·Fzact_(—)1/sqrt(1+Fy0_(—)1²/(tan θ·μestm·Fzact_(—)1)²)  Expression 44

The expression 44 and the expression 42 are the expressions fordetermining Fxmmax_1. If Fxcand_1 is a positive value, then Fxmmax_1will be a value obtained by reversing the sign of the computation resultof the right side of expression 44.

On the remaining wheels W2 to W4, Fxmmax_n (n=1, 2, 3) can be calculatedin the same manner as that described above. Regarding the rear wheels W3and W4, the actual steering angle is zero, so that the values thereofare unnecessary.

Returning to the explanation of the flowchart of FIG. 25, from S306 toS314, the same processing as the processing from S104 to S112 of FIG. 19in the aforesaid first embodiment is carried out, thereby determiningthe target n-th wheel driving/braking force Fxcmd_n.

Subsequently, the procedure proceeds to S316 wherein a slip ratioassociated with Fxcmd_n is determined, and it is determined as thetarget n-th wheel target slip ratio Scmd_n. In this case, the targetn-th wheel slip ratio Scmd_n is determined on the basis of, for example,a map which shows the relationship between the driving/braking forcesand slip ratios of the n-th wheel Wn and which is established inadvance. The map used here is a map corresponding to a set of [estm andthe actual side slip angle βf_act or βr_act (or Fy0 _(—) n) of the n-thwheel Wn.

The target n-th wheel driving/braking force Fxcmd_n is determined by theprocessing from S300 to S316 described above such that conditionsequivalent to the aforesaid conditions (1) to (3) are satisfied. And, ifno target n-th wheel driving/braking force Fxcmd_n that satisfies allthe conditions (1) to (3) can be determined, then the target n-th wheeldriving/braking force Fxcmd_n is determined such that a condition with ahigher priority rank is preferentially satisfied.

Fifth Embodiment

A fifth embodiment of the present invention will now be explained withreference to FIG. 27. The present embodiment differs from the aforesaidthird embodiment only partly in processing, so that the explanation willbe focused mainly on the different aspect, and the explanation of thesame portions will be omitted. In the explanation of the presentembodiment, the same constituent portions or the same functionalportions as those of the third embodiment will be assigned the samereference characters as those of the third embodiment.

The present embodiment differs from the third embodiment only in theprocessing by the optimum target n-th driving/braking force determiner241 b _(—) n (n=1, 2, 3, 4) of the actuator operation target valuesynthesizer 24 shown in FIG. 23 described above. In this case, accordingto the present embodiment, although not shown, each optimum target n-thdriving/braking force determiner 241 b _(—) n receives an estimatedfriction coefficient μestm and an actual road surface reaction force ofthe n-th wheel Wn (an actual driving/braking force Fxact_n, an actuallateral force Fyact_n, and an actual ground contact load Fzact_n) inaddition to the FF total n-th wheel driving/braking force FFtotal_n andthe unlimited n-th wheel driving/braking force Fxdmd_n. Then, eachoptimum target n-th driving/braking force determiner 241i b_(—) npresumes the relationship between the driving/braking force and thelateral force of the n-th wheel Wn represented by the expression 40 onthe basis of the estimated friction coefficient μestm and the actualroad surface reaction force of the n-th wheel Wn, which have been inputthereto. Further, by using the presumed relationship, a target n-thwheel driving/braking force Fxcmd_n and a target n-th wheel slip ratioScmd_n are determined.

FIG. 27 is a flowchart showing the processing by each optimum targetn-th driving/braking force determiner 241 b _(—) n in the presentembodiment. The following will give an explanation thereof. First, inS400, the same processing as that in S300 of FIG. 25 described above iscarried out to determine the value of Fy0 _(—) n of expression 40.

Subsequently, the procedure proceeds to S402 wherein a lateral forceFyff_n associated with the FF total target n-th wheel driving/brakingforce FFtotal_n is determined. More specifically, the values ofFFtotal_n, Fzact_n, and μestm are substituted into Fx_n, Fz_n, and μ,respectively, of the expression 40, and the value determined in S400 issubstituted into Fy0 _(—) n of expression 40 (in other words, by theexpression shown in the figure) to effect a solution on Fy_n, therebydetermining the value of Fyff_n.

Subsequently, the procedure proceeds to S404 wherein the moment in theyaw direction generated about the center-of-gravity point G of theactual vehicle 1 by the resultant force of a driving/braking forceFFtotal_n and a lateral force Fyff_n of the n-th wheel Wn is determined,and the determined moment is defined as the n-th wheel FF moment Mff_n.This processing is carried out in the same manner as the processing inS204 of FIG. 24 described above. The Mff_n determined as described abovecorresponds to an n-th wheel feedforward required moment (a requiredmoment when Mfbdmd_n=0).

Subsequently, the procedure proceeds to S406 wherein the Mff_ndetermined as described above and the FB target brake moment Mfbdmd_nare added up thereby to calculate a temporary target moment candidateMcand_n, which is a temporary target value of a moment (a moment in theyaw direction) about the center-of-gravity point G of the actual vehicle1 by a road surface reaction force of the n-th wheel Wn.

Subsequently, the procedure proceeds to S408 wherein a driving/brakingforce Fx_n of a road surface reaction force that causes a moment in theyaw direction generated about the center-of-gravity point G of theactual vehicle 1 by a road surface reaction force (the resultant forceof the driving/braking force Fx_n and the lateral force Fy_n) of then-th wheel Wn to become maximum toward the same polarity as the polarityof the feedback yaw moment basic required value Mfbdmd is determined,using the expression 40 as the restrictive condition, and the determineddriving/braking force Fx_n is defined as an n-th wheel driving/brakingforce at the generation of a maximum moment Fxmmax_n. This processing isthe same as the processing in S304 of FIG. 25 described above.

Subsequently, the procedure proceeds to S410 wherein Fx_n at which themoment in the yaw direction generated about the center-of-gravity pointG of the actual vehicle 1 by a road surface reaction force of the n-thwheel Wn (the resultant force of the driving/braking force Fx_n and thelateral force Fy_n) agrees or becomes closest to Mcand_n is determined,using the expression 40 as the restrictive condition, and the determinedFx_n is defined as a candidate of the driving/braking force of the n-thwheel Wn Fxcand_n (the n-th wheel driving/braking force candidateFxcand_n). The Fxcand_n is determined, however, such that neither0>Fxmmax_n>Fxcand_n nor 0<Fxmmax_n<Fxcand_n takes place (in other words,such that the sign of Fxcand_n is different from the sign of Fxmmax_n orthe absolute value of Fxcand_n is not more than the absolute value ofFxmmax_n).

In this case, if the absolute value of Mcand_n is the absolute value ormore of a maximum moment associated with Fxmmax_n, then Fxmmax_n isdetermined as Fxcand n.

Further, if the absolute value of Mcand_n is smaller than the absolutevalue of the maximum moment associated with Fxmmax_n, then, from amongthe pairs of Fx_n and Fy_n that satisfy the relationship of expression40, a pair of Fx_n and Fy_n which causes a moment in the yaw directionto be generated about the center-of-gravity point G of the actualvehicle 1 by the resultant force thereof to agree with Mcand_n isexploratively determined. Then, the determined Fx_n is determined asFxcand_n. Incidentally, for the front wheels W1 and W2, this processinguses not only expression 40 but also the value of the actual front wheelsteering angle δf_act.

In this case, there are two pairs of Fx_n and Fy_n that cause the momentin the yaw direction generated about the center-of-gravity point G ofthe actual vehicle 1 by the resultant force of Fx_n and Fy_n to agreewith Mcand_n. If Fxmmax_n<0, then the Fx_n which is expressed asFx_n>Fxmmax_n is determined as Fxcand_n, and if Fxmmax_n>0, then theFx_n which is expressed as Fx_n<Fxmmax n is determined as Fcand_n.

By such processing in S410, Fxcand_n is determined such that the momentin the yaw direction generated about the center-of-gravity point of theactual vehicle 1 agrees with or becomes closest to Mcand_n, whilepreventing 0>Fxmmax_n>Fxcand_n or 0<Fxmmax_n<Fxcand_n from taking place,within a range in which expression 40 is satisfied.

Subsequently, the procedure proceeds to S412 wherein it is determinedwhether 0>FFtotal_n>Fxcand_n applies. If the determination result isYES, then the procedure proceeds to S414 wherein the value of Fxcand_nis substituted into Fxcmd_n. If the determination result in S412 is NO,then the procedure proceeds to S416 wherein the value of FFtotal_n issubstituted into Fxcmd_n. Thus, the target n-th wheel driving/brakingforce Fxcmd is determined.

Subsequently, the procedure proceeds to S418 wherein a slip ratioassociated with Fxcmd_n is determined as a target n-th wheel slip ratioScmd_n. This processing is the same as the processing in S316 of FIG.25.

The above has explained in detail the processing by the optimum targetn-th driving/braking force determiner 241 b _(—) n in the presentembodiment.

Supplementally, the present embodiment uses, in place of condition (3)in the aforesaid first embodiment, the same condition as condition (3)′explained in relation to the aforesaid third embodiment. In this case,however, the wheel characteristics relationship in the aforesaid thirdembodiment corresponds to the elliptical function of the expression(40). Therefore, condition (3)′ in the present embodiment is, moreprecisely, a condition that a value within the range of values ofdriving/braking forces that can be generated in the n-th wheel Wnaccording to the expression (40) is obtained, and a moment in the yawdirection generated about the center-of-gravity point G of the actualvehicle 1 by a road surface reaction force that has a driving/brakingforce component equal to Fxcmd_n among the road surface reaction forcesthat can be generated in the n-th wheel Wn according to the wheelcharacteristics relationship agrees with or is close to the aforesaidMcand_n as much as possible (the absolute value of a difference fromMcand_n is minimized). In addition, among this condition (3)′ and theconditions (1) and (2), the condition (1) is defined as thehighest-priority condition and condition (2) is defined as the next-rankcondition, and then the target n-th wheel driving/braking force Fxcmd_nis determined such that these conditions (1), (2), and (3)′ aresatisfied according to the order of priority. In this case, Fxcmd_n isdetermined by the processing up to S410 described above such thatcondition (3)′ is satisfied as much as possible within a range in whichcondition (2) can be eventually satisfied. Further, Fxcmd_n isdetermined such that the highest-priority condition (1) is satisfied bycarrying out the processing in S412 to S416.

The following will explain some modifications of the first to the fifthembodiments described above.

[Modification 1]

In the first to the fifth embodiments described above, the reference yawrate γd and the reference vehicle center-of-gravity point side slipangle βd have been used as the reference state amounts; alternatively,however, the following may be applied. For example, only the referenceyaw rate γd may be sequentially determined as a reference state amountby a reference dynamic characteristics model. Then, the referencedynamic characteristics model and the actuator devices 3 of the actualvehicle 1 may be manipulated to approximate the state amount error γerr,which is a difference between the actual yaw rate γact and the referenceyaw rate γd thereof, to zero. In this case, in place of the referencedynamic characteristics model 16 represented by the aforesaid expression(1), a reference dynamic characteristics model 56 shown in FIG. 28, forexample, may be used to sequentially determine the reference yaw rateγd.

The following will explain in detail the reference dynamiccharacteristics model 56 in FIG. 28. The reference dynamiccharacteristics model 56 sequentially receives, at each controlprocessing cycle, a steering angle θh, an actual traveling velocityVact, and a virtual external force moment (a moment in the yawdirection) Mvir as a control input for manipulating the referencedynamic characteristics model 56 (a control input for approximating γerrto zero). Incidentally, θh and Vact take latest values (current timevalues) and Mvir takes a last time value.

Then, the reference dynamic characteristics model 56 first determines astabilization target yaw rate γ∞ from the input θh and Vact according toa map for determining stabilization target values 56 a. Thestabilization target yaw rate γ∞ means a convergence value of a yaw rateof a model vehicle (a vehicle on the reference dynamic characteristicsmodel 56 in the present embodiment) when the θh and Vact are steadilymaintained at their input values. Incidentally, the map for determiningstabilization target values 56 a is desirably set beforehand on thebasis of the estimated friction coefficient μestm.

Subsequently, the last time value of the reference yaw rate γd (thevalue determined at the last time control processing cycle from thereference dynamic characteristics model 56) and the stabilization targetyaw rate γ∞ are input to a flywheel follow-up law 56 b. Then, a flywheelFB moment Mfb is determined by the flywheel follow-up control law 56 b.Here, according to the present embodiment, a rotational motion of themodel vehicle in the yaw direction thereof is expressed in terms of arotational motion of a horizontal flywheel (a flywheel whose rotationalaxis is an axis in the vertical direction). Then, the rotational angularvelocity of the flywheel is output as a reference yaw rate γd.

Then, the flywheel follow-up law 56 b determines the flywheel FB momentMfb as a moment to be input to the flywheel (a control input of thedimension of an external force to be input to the flywheel) according toa feedback control law (e.g., a proportional law or aproportional-derivative law) such that the rotational angular velocityof the flywheel, that is, the reference yaw rate γd, is converged to thestabilization target yaw rate γ∞.

Subsequently, the reference dynamic characteristics model 56 adds thevirtual external force moment Mvir to the Mfb by an adder 56 c todetermine an input (moment) to the flywheel. Then, the input moment isdivided by an inertial moment J of the flywheel in a processor 56 dthereby to determine a rotational angular acceleration of the flywheel.Further, a value obtained by integrating the rotational angularacceleration (the integration is expressed by an operator “1/s” in thefigure) is output as a reference yaw rate γd.

The value of the inertial moment J of the flywheel may be set to a valuewhich is the same or substantially the same as, for example, the valueof an inertial moment about the center-of-gravity point G of the actualvehicle 1. Alternatively, a value identified while the actual vehicle 1is traveling may be used.

The above has explained the details of the processing by the referencedynamic characteristics model 56.

Supplementally, the processing other than that by the reference dynamiccharacteristics model 56 in this modification 1 may be the same as, forexample, the aforesaid first embodiment. However, in the processing bythe virtual external force determiner 20 a of the aforesaid firstembodiment, Mvir is determined by setting, for example, βerr, βda, andβover to zero, and the Mvir is fed back to the reference dynamiccharacteristics model 56. In this case, regarding γda, the value of ayaw rate of the vehicle on the reference dynamic characteristics model56 after predetermined time may be predicted from, for example, thecurrent time values of Vact and θh and a temporary value Mvirtmp of Mvirbased on γerr, and the predicted value may be used as γda.Alternatively, for example, the current time value of γact or thelinearly coupled value of γact and γd may be used as γda. Further, inthe processing by an actuator operation FB target value determiner 20 b,the processing explained in the aforesaid first embodiment is carriedout by setting βerr to zero. In this modification 1, the processing bythe reference manipulated variable determiner 14 is unnecessary. Therest may be the same as the processing explained in the aforesaid firstembodiment.

[Modification 2]

In the first to the fifth embodiments described above, the vehiclecenter-of-gravity point side slip angle β and the yaw rate γ have beenused as the basal state amount related to the translational motion inthe lateral direction of the vehicle (the actual vehicle 1 and the modelvehicle) and the basal state amount related to a rotational motion (asthe first state amounts in the present invention); alternatively,however, other state amounts may be used. More specifically, thedescription of a vehicle motion may be transformed from a system basedon β and γ into a system based on a set of other state amounts by anappropriate transformation matrix.

For example, a vehicle side slip velocity Vy, which is the side slipvelocity (a lateral component of the traveling velocity Vact) of thecenter-of-gravity point of the vehicle, may be used in place of avehicle center-of-gravity point side slip angle β. Supplementally, if achange in the traveling velocity Vact of the vehicle is slow as comparedwith the vehicle center-of-gravity point side slip angle β or the yawrate γ and the traveling velocity Vact can be regarded as beingconstant, then β and dβ/dt (a temporal differential value of β) can beconverted into Vy and dVy/dt (a temporal differential value of Vy),respectively, according to the following expressions 50a and 50b.

Vy=Vact·β  Expression 50a

dVy/dt=Vact·dβ/dt   Expression 50b

Further, for example, a vehicle side slip acceleration αy, which is aside slip acceleration of the center-of-gravity point of the vehicle (atemporal change rate of Vy) and the yaw rate γ may be used as the basalstate amounts.

Supplementally, the vehicle side slip acceleration αy denotes thetemporal differential value of the vehicle side slip velocity Vy=Vact·β.In other words, the following expression 51 holds.

αy=d(Vact·β)/dt=dVact/dt·β+Vact·d/dt   Expression 51

Further, if a change in the traveling velocity Vact of the vehicle isslow as compared with the side slip angle β or the yaw rate γ, and Vactcan be regarded as being constant (if it can be regarded as dVact/dt≈0),then the following expression 52 approximately holds on the basis of theaforesaid expression 01 and expression 51.

αy=Vact·dβ/dt=a11·Vact·β+a12·Vact·γ  Expression 52

Hence, a system using β and γ as its bases is transformed into a systemusing αy and γ as its bases according to a transformation expressionindicated by the following expression 53.

$\begin{matrix}\lbrack {{Mathematical}\mspace{14mu} {expression}{\mspace{11mu} \;}10} \rbrack & \; \\{\begin{bmatrix}{\alpha \; y} \\\gamma\end{bmatrix} = {\begin{bmatrix}{a\; {11 \cdot {Vact}}} & {a\; {12 \cdot {Vact}}} \\0 & 1\end{bmatrix} \cdot \begin{bmatrix}\beta \\\gamma\end{bmatrix}}} & {{Expression}\mspace{14mu} 53}\end{matrix}$

As described above, the description of a vehicle motion can betransformed from a system using β and γ as its bases into a system usingVy and γ as its bases, a system using αy and γ as its bases, or the likeby an appropriate matrix. And, when the bases of vehicle motions aretransformed as described above, the element values of a matrix relatedto a state amount (a yaw rate and a vehicle center-of-gravity point sideslip angle) explained in the aforesaid first to fifth embodiments willbe different from those in the embodiments, but for the rest, “thevehicle center-of-gravity point side slip angle” in each of theaforesaid embodiments may be reread to “the vehicle side slip velocityVy” or “the vehicle side slip acceleration.” Thus, an embodiment thatuses a pair of Vy and γ or a pair of αy and γ as a state amount can beconstructed in the same manner as that of the aforesaid first to fifthembodiments.

In place of the vehicle side slip acceleration ay, a lateralacceleration αγ′(=αy+Vact·γ) obtained by adding a centripetalacceleration of the vehicle (=Vact·γ) to the vehicle side slipacceleration αy may be used.

Further, a side slip angle, a side slip velocity, a side slipacceleration or a lateral acceleration of the vehicle at a positionother than the center-of-gravity point (e.g., a position on a rearwheel) may be used in place of the side slip angle β or the side slipvelocity Vy at the center-of-gravity point of the vehicle. In this casealso, the description of a vehicle motion can be transformed from asystem using the vehicle center-of-gravity point side slip angle β andthe yaw rate γ as its bases into a system using the side slip angle or aside slip velocity, a side slip acceleration or a lateral accelerationof the vehicle at a position other than the center-of-gravity point ofthe vehicle, and the yaw rate γ as its bases by an appropriate matrix.

Further, for a restriction object amount in the FB distribution law 20,a predicted value or a current time value (a latest value) or a filteredvalue of a side slip velocity or a side slip acceleration or a lateralacceleration of the center-of-gravity point may be used in place of thevehicle center-of-gravity point side slip angle β of the actual vehicle1 or the model vehicle. Further, a predicted value or a current timevalue (a latest value) or a filtered value of a side slip angle or aside slip velocity, a side slip acceleration or a lateral accelerationof the vehicle at a position other than the center-of-gravity point ofthe vehicle may be used as a restriction object amount.

[Modification 3]

In the first to the fifth embodiments described above, the virtualexternal forces Mvir and Fvir have been used as the control inputs formanipulating the model for bringing the state amount errors γerr andβerr close to zero; however, the control inputs for manipulating thevehicle model are not limited to virtual external forces. For example,all wheels of the model vehicle may be steering control wheelsregardless of whether the actual vehicle 1 is equipped with a steeringdevice that permits steering of all the wheels W1 to W4. And, thesteering angles of the steering control wheels of the model vehicle andthe driving/braking forces of the wheels of the model vehicle may bemanipulated such that a compensation amount (a correction requiredamount) of a road surface reaction force corresponding to a virtualexternal force is produced in the model vehicle (so as to eventuallyapproximate state amount errors to zero). In this case, if the referencedynamic characteristics model is a linear system (a system that exhibitsno saturation characteristics in road surface reaction force on thereference dynamic characteristics model), then an advantage equivalentto that obtained by imparting a virtual external force to a modelvehicle can be provided by manipulating the steering angles of thesteering control wheels of the model vehicle and the driving/brakingforces of the wheels of the model vehicle.

For example, expression 60 given below may be used instead of theaforesaid expression 01 as the expression representing the dynamiccharacteristics of a reference dynamic characteristics model.

$\begin{matrix}\lbrack {{Mathematical}\mspace{14mu} {expression}\mspace{14mu} 11} \rbrack & \; \\{{\frac{\;}{t}\begin{bmatrix}{\beta \; d} \\{\gamma \; d}\end{bmatrix}} = {\begin{bmatrix}{a\; 11} & {a\; 12} \\{a\; 21} & {a\; 22}\end{bmatrix} \cdot {\quad{\begin{bmatrix}{\beta \; d} \\{\gamma \; d}\end{bmatrix} + {\begin{bmatrix}{b\; 1} \\{b\; 2}\end{bmatrix} \cdot ( {{\delta \; {f\_ ltd2}} + {\delta f\_ fb}} )} + {\begin{bmatrix}{b\; 3} \\{b\; 4}\end{bmatrix} \cdot {\delta r\_ fb}} + {b\; {5 \cdot \begin{bmatrix}0 \\{{{Fx}\; 2{fb}} - {{Fx}\; 1{fb}}}\end{bmatrix}}} + {b\; {6 \cdot \begin{bmatrix}0 \\{{{Fx}\; 4{fb}} - {{Fx}\; 3\; {fb}}}\end{bmatrix}}}}}}} & {{Expression}\mspace{14mu} 60}\end{matrix}$

The reference dynamic characteristics model represented by thisexpression 60 is a model which uses a compensation amount of a steeringangle of a front wheel δf_fb, a compensation amount (a correctionrequired amount) of a steering angle of a rear wheel δr_fb, andcompensation amounts (correction required amounts) of thedriving/braking forces of the first to the fourth wheels Fx1 fb, Fx2 fb,Fx3 fb, and Fx4 fb of the model vehicle as the feedback control inputsfor manipulating the model. Incidentally, a11, a12, a21, a22, b1, and b2in expression 60 may be the same as those given in the note of theexpression 01. Further, b3 and b4 may be, for example, b3=2·Kr/(m·Vd)and b4=2·Lr·Kr/I. The fourth term of the right side of expression 60indicates a moment generated about the center-of-gravity point of themodel vehicle by the compensation amounts Fx1 fb and Fx2 fb of thedriving/braking forces of the front wheels of the model vehicle (thismeans a moment generated about the center-of-gravity point of the modelvehicle when the driving/braking force of Fx1 fb is generated in thefront wheel W1 of the model vehicle provided with the four wheels W1 toW4 as shown in the aforesaid FIG. 13 and the driving/braking force ofFx2 fb is generated in the front wheel W2). Further, the fifth termindicates a moment generated about the center-of-gravity point of themodel vehicle by the compensation amounts Fx3 fb and Fx4 fb of thedriving/braking forces of the rear wheels of the model vehicle (thismeans a moment generated about the center-of-gravity point of the modelvehicle when the driving/braking force of Fx3 fb is generated in therear wheel W3 of the model vehicle provided with the four wheels W1 toW4 as shown in the aforesaid FIG. 13 and the driving/braking force ofFx4 fb is generated in the rear wheel W4). Hence, coefficients b5 and b6of the fourth term and the fifth term are coefficients defined on thebasis of at least the tread of the front wheels and the tread of therear wheels, respectively, of the model vehicle. The coefficients may becorrected on the basis of the steering angles of the front wheels or thesteering angles of the rear wheels of the model vehicle.

When the reference dynamic characteristics model represented by suchexpression 60 is used, the compensation amount of a steering angle of afront wheel δf_fb and the compensation amount of a steering angle of arear wheel δr_fb may be determined by using, for example, expressions61a and 61b shown below. Expression 61a is an expression correspondingto the expression 15 and expression 61b is an expression correspondingto the expressions 17, 18a, and 18b.

$\begin{matrix}\lbrack {{Mathematical}\mspace{14mu} {expression}\mspace{14mu} 12} \rbrack & \; \\{{\begin{bmatrix}{\delta \; {f\_ fbtmp}} \\{\delta \; {r\_ fbtmp}}\end{bmatrix} = {\begin{bmatrix}{{Kmdlstrtmp}\; 11} & {{Kmdlstrtmp}\; 12} \\{{Kmdlstrtmp}\; 21} & {{Kmdlstrtmp}\; 22}\end{bmatrix} \cdot \begin{bmatrix}{\beta \; {err}} \\{\gamma \; {err}}\end{bmatrix}}}} & {{Expression}\mspace{14mu} 61\; a} \\{\begin{bmatrix}{\delta \; {f\_ fb}} \\{\delta \; {r\_ fb}}\end{bmatrix} = {\begin{bmatrix}{\delta \; {f\_ fbtmp}} \\{\delta \; {r\_ fbtmp}}\end{bmatrix} - {\quad{\begin{bmatrix}{{Kmdlstrov}\; 11} & {{Kmdlstrov}\; 12} \\{{Kmdlstrov}\; 21} & {{Kmdlstrov}\; 22}\end{bmatrix} \cdot \begin{bmatrix}{\beta \mspace{11mu} {over}} \\{\gamma \mspace{11mu} {over}}\end{bmatrix}}}}} & {{Expression}\mspace{14mu} 61\; b}\end{matrix}$

δf_fbtmp and δr_fbtmp mean the temporary value of a compensation amountof a front wheel steering angle and a temporary value of a compensationamount of a rear wheel steering angle, respectively, and βerr, γerr,βover, and γover are the same as those explained in the aforesaid firstembodiment.

Further, the compensation amounts (the correction required amounts) ofthe driving/braking forces of the first to the fourth wheels Fx1 fb, Fx2fb, Fx3 fb, and Fx4 fb of the model vehicle or a difference in thecompensation amount of the driving/braking forces between the frontwheels (Fx2 fb−Fx1 fb) and a difference in the compensation amount ofthe driving/braking forces between the rear wheels (Fx2 fb−Fx1 fb) maybe set to, for example, zero.

[Other Modifications]

In the first to the third embodiments described above, the processing byeach optimum target n-th driving/braking force determiner 241 a _(—) nor 241 b _(—) n (n=1, 2, 3, 4) of the actuator operation target valuesynthesizer 24 has used the actual front wheel side slip angle βf_actand the actual rear wheel side slip angle βr_act. Instead of them,however, the actual vehicle center-of-gravity point side slip angle βactmay be used. Alternatively, instead of βf_act and βr_act, respectively,the front wheel side slip angle βf_d and the rear wheel side slip angleβr_d, respectively, of the model vehicle may be used, or instead ofβf_act and βr_act, the vehicle center-of-gravity point side slip angleβd of the model vehicle may be used. Alternatively, the weighted meanvalues of βf_act and βr_act, respectively, of the actual vehicle 1 andβf_d and βr_d, respectively, of the model vehicle may be used in placeof βf_act and βr_act, respectively, or a weighted mean value of βact ofthe actual vehicle 1 and βd of the model vehicle may be used in place ofβf_act and βr_act. In this case, the weights may be provided with afrequency characteristic (e.g., a frequency characteristic thatfunctions as a phase compensating element).

Input values and output values (detected values, estimated values,target values, and the like) to and from the processors in the first tothe fifth embodiments described above may be passed through filters(low-pass filters, high-pass filters, phase compensating elements, orthe like), as necessary.

Further, the processing function sections of the controller 10 maytransform processing or change the order of processing such that theymay be equivalent or approximately equivalent to the first to the fifthembodiments.

The limiters whose input/output relationships are indicated by polygonalline graphs may be replaced by limiters whose input/output relationshipsare indicated by, for example, S-shaped graphs.

In order to enhance the accuracy of the reference dynamiccharacteristics models, the models may be constructed by taking airresistance or the slope angles of road surfaces or the like intoaccount.

The gains used in the aforesaid embodiments are desirably changed asnecessary according to the actual traveling velocity Vact, the estimatedfriction coefficient μestm, and the like.

If the steering device 3B is an active steering device, then thesteering device 3B alone may be used as the actuator device thatconducts the feedback control based on the state amount errors, such asγerr and βerr (the first state amount errors in the present invention).

If the suspension device 3C is an active suspension device, then, forexample, the angle of a posture of a vehicle body in the roll direction(hereinafter referred to as the roll angle) or the angular velocitythereof may be used as the first state amount of the actual vehicle 1and the model vehicle, and at least one of the difference between theangular velocity of the roll angle of the actual vehicle 1 and theangular velocity of the roll angle of the model vehicle and a differencebetween the roll angle of the actual vehicle 1 and the roll angle of themodel vehicle may be defined as the first state amount error, andfeedback control based on the error may be carried out on the suspensiondevice 3C. In this case, as the second state amount in the presentinvention, the roll angle, for example, is ideally used.

In the first to the fifth embodiments described above, the target n-thwheel driving/braking force Fxcmd_n and the target n-th wheel slip ratioScmd_n have been determined such that conditions (1), (2) and (3) orconditions (1), (2) and (3)′ are satisfied according to the priorityranks thereof. Alternatively, however, Fxcmd_n and Scmd_n may bedetermined such that, for example, only condition (3) or (3)′ issatisfied. Alternatively, Fxcmd_n and Scmd_n may be determined such thatonly two conditions, namely, one of conditions (1) and (2) and condition(3) or (3)′ are satisfied according to the priority ranks thereof.

Further, regarding the range that limits the driving/braking forces orslip ratios of the wheels W1 to W4 to satisfy the aforesaid condition(1) or (2), instead of specifying “xx or less” (xx means a certainboundary value), the range may be specified by “not more than a valueobtained by multiplying xx by C1,” where C1 means a correctioncoefficient and it is set to a value in the vicinity of 1.

The aforesaid first to the fifth embodiments have been explained bytaking the four-wheeled vehicle 1 as an example; the present invention,however, can be applied also to a vehicle, such as a two-wheeled motorvehicle.

Industrial Applicability

As is obvious from the above explanation, the present invention isusefully applied to allow motions of an automobile or a two-wheeledmotor vehicle to be controlled to desired motions with high robustness.

BRIEF DESCRIPTION OF THE DRAWINGS

[FIG. 1] It is a block diagram showing a schematic construction of avehicle in an embodiment of the present invention.

[FIG. 2] It is a functional block diagram schematically showing anoverall control processing function of a controller provided in avehicle in a first embodiment of the present invention.

[FIG. 3] It is a diagram showing the structure of a vehicle on areference dynamic characteristics model (vehicle model) in the firstembodiment.

[FIG. 4] It is a functional block diagram showing the details of aprocessing function of a reference manipulated variable determiner inthe first embodiment.

[FIG. 5] It is a graph for explaining the processing by a limiter forpreventing excessive centrifugal forces, which is provided in thereference manipulated variable determiner in the first embodiment.

[FIG. 6] It is a graph for explaining another example of the processingby the limiter for preventing excessive centrifugal forces in the firstembodiment.

[FIG. 7] It is a graph for explaining still another example of theprocessing by the limiter for preventing excessive centrifugal forces inthe first embodiment.

[FIG. 8] It is a functional block diagram showing another example ofprocessing for determining a second limited front wheel steering angleδf_ltd2 in the reference manipulated variable determiner in the firstembodiment.

[FIG. 9] It is a functional block diagram showing the processingfunction of an FB distribution law in the first embodiment.

[FIG. 10] It is a functional block diagram showing another example ofthe processing by a virtual external force determiner in the firstembodiment.

[FIG. 11] It is a graph for explaining another example of the processingby a γβ limiter in the first embodiment.

[FIG. 12] It is a functional block diagram showing the processing by anactuator operation FB target value determiner in the first embodiment.

[FIG. 13] It is a diagram for explaining a variable used in theprocessing by the actuator operation FB target value determiner in thefirst embodiment.

[FIG. 14] FIGS. 14( a) and (b) are graphs showing distribution gainsetting examples used in the processing by the actuator operation FBtarget value determiner in the first embodiment.

[FIG. 15] FIGS. 15( a) to (e) are diagrams illustrating the maps usedwith another example of the processing by the actuator operation FBtarget value determiner in the first embodiment.

[FIG. 16] FIGS. 16( a) to (e) are diagrams illustrating the maps usedwith still another example of the processing by the actuator operationFB target value determiner in the first embodiment.

[FIG. 17] It is a functional block diagram showing the processing by anFF law in the first embodiment.

[FIG. 18] It is a functional block diagram showing the processing by anactuator operation target synthesizer in the first embodiment.

[FIG. 19] It is a flowchart showing the processing by an optimum targetn-th wheel driving/braking force determiner provided in the actuatoroperation target synthesizer in the first embodiment.

[FIG. 20] It is a functional block diagram showing the processing by anoptimum target active steering angle determiner provided in the actuatoroperation target synthesizer in the first embodiment.

[FIG. 21] It is a functional block diagram showing the processing by avirtual external force determiner of an FB distribution law in a secondembodiment.

[FIG. 22] It is a functional block diagram showing the processing by anactuator operation FB target value determiner in a third embodiment.

[FIG. 23] It is a functional block diagram showing the processing by anactuator operation target value synthesizer in the third embodiment.

[FIG. 24] It is a flowchart showing the processing by an optimum targetn-th wheel driving/braking force determiner provided in the actuatoroperation target synthesizer in the third embodiment.

[FIG. 25] It is a flowchart showing the processing by an optimum targetn-th wheel driving/braking force determiner provided in the actuatoroperation target synthesizer in a fourth embodiment.

[FIG. 26] It is a diagram for explaining an example of the processing inS304 of FIG. 25.

[FIG. 27] It is a flowchart showing the processing by an optimum targetn-th wheel driving/braking force determiner provided in an actuatoroperation target synthesizer in a fifth embodiment.

[FIG. 28] It is a functional block diagram showing the processing by areference dynamic characteristics model in modification 1 of theembodiments of the present invention.

1. A vehicle control device having a drive manipulated variabledetecting means which detects a drive manipulated variable thatindicates a drive manipulation state of a vehicle driven by a driver ofthe vehicle having a plurality of wheels, an actuator device provided inthe vehicle so as to permit the manipulation of a predetermined motionof the vehicle, and an actuator device control means which sequentiallycontrols an operation of the actuator device, the vehicle control devicecomprising: an actual state amount grasping means for detecting orestimating a first actual state amount, which is a value of apredetermined first state amount related to a predetermined motion of anactual vehicle; a model state amount determining means for determining afirst model state amount, which is a value of the first state amountrelated to a predetermined motion of a vehicle on a vehicle modelestablished beforehand as a model expressing dynamic characteristics ofthe vehicle, on the basis of at least the detected drive manipulatedvariable; a state amount error calculating means for calculating a firststate amount error, which is a difference between the detected orestimated first actual state amount and the determined first model stateamount; and an actual vehicle state amount error response control meansand a model state amount error response control means, whichrespectively determine an actual vehicle actuator operation controlinput for operating the actuator device of the actual vehicle and avehicle model operation control input for manipulating the predeterminedmotion of the vehicle on the vehicle model on the basis of at least thecalculated first state amount error such that the first state amounterror is approximated to zero, wherein the actuator device control meansis a means which controls the operation of the actuator device on thebasis of at least the determined actual vehicle actuator operationcontrol input, the model state amount determining means is a means whichdetermines the first model state amount on the basis of at least thedetected drive manipulated variable and the determined vehicle modeloperation control input, the actual vehicle state amount error responsecontrol means comprises a means which determines an actual vehiclefeedback required amount by a feedback control law on the basis of atleast the first state amount error and a means which determines theactual vehicle actuator operation control input on the basis of at leastthe actual vehicle feedback required amount, and the means whichdetermines the actual vehicle actuator operation control input is ameans which determines the actual vehicle actuator operation controlinput by using a predetermined value set beforehand in a predetermineddead zone in place of the actual vehicle feedback required amount in acase where the actual vehicle feedback required amount lies in the deadzone, and the model state amount error response control means is a meanswhich determines the vehicle model operation control input such that atleast the first state amount error is approximated to zero regardless ofwhether the actual vehicle feedback required amount lies in the deadzone or not.
 2. The vehicle control device according to claim 1, whereinthe first state amount includes a state amount related to a rotationalmotion of the vehicle in a yaw direction, the actuator devices includean actuator device capable of manipulating at least a difference betweenright and left driving/braking forces, which is a difference between thedriving/braking forces of a pair of right and left wheels of the actualvehicle, and the actual vehicle actuator operation control inputincludes at least one of the target driving/braking forces of the pairof right and left wheels and a target slip ratio, the manipulatedvariable of the actuator device associated with the targetdriving/braking forces or the target slip ratio, and the manipulatedvariable of the difference between the right and left driving/brakingforces.
 3. The vehicle control device according to claim 1, comprising ameans for determining the amount of deviation of a restriction objectamount, the value of which is defined by at least one of a second stateamount related to a motion of the actual vehicle and a second stateamount related to a motion of the vehicle on the vehicle model, from apredetermined permissible range, wherein the model state amount errorresponse control means determines the vehicle model operation controlinput such that the first state amount error and the determined amountof deviation approximate to zero independently of whether the actualvehicle feedback required amount exists in the dead zone or not.
 4. Thevehicle control device according to claim 1, comprising a means fordetermining the amount of deviation of a restriction object amount, thevalue of which is defined by at least one of a second state amountrelated to a motion of the actual vehicle and a second state amountrelated to a motion of the vehicle on the vehicle model, from apredetermined permissible range, wherein the means for determining theactual vehicle feedback required amount is a means which determines theactual vehicle feedback required amount by a feedback control law suchthat the first state amount error and the determined amount of deviationare approximated to zero.
 5. The vehicle control device according toclaim 1, comprising a means for determining the amount of deviation of arestriction object amount, the value of which is defined by at least oneof a second state amount related to a motion of the actual vehicle and asecond state amount related to a motion of the vehicle on the vehiclemodel, from a predetermined permissible range, and a means fordetermining a feedback auxiliary required amount by a feedback controllaw such that the amount of deviation is approximated to zero, whereinthe means for determining the actual vehicle feedback required amount isa means for determining the actual vehicle feedback required amount bythe feedback control law such that the first state amount error isapproximated to zero, and the means for determining the actual vehicleactuator operation control input is a means which determines the actualvehicle actuator operation control input on the basis of a valueobtained by correcting the predetermined value on the basis of at leastthe feedback auxiliary required amount in the case where the actualvehicle feedback required amount lies in the dead zone, and determinesthe actual vehicle actuator operation control input on the basis of avalue obtained by correcting the actual vehicle feedback required amounton the basis of at least the feedback auxiliary required amount in thecase where the actual vehicle feedback required amount does not lie inthe dead zone.
 6. The vehicle control device according to claim 3,wherein the first state amount includes a state amount related to arotational motion in the yaw direction of the vehicle, and therestriction object amount includes at least one of a latest value of astate amount related to a lateral translational motion of the actualvehicle or the vehicle on the vehicle model or a value obtained byfiltering the state amount or a future predicted value of the stateamount, and a latest value of a state amount related to a rotationalmotion in the yaw direction of the actual vehicle or the vehicle on thevehicle model or a value obtained by filtering the state amount or afuture predicted value of the state amount.
 7. The vehicle controldevice according to claim 4, wherein the first state amount includes astate amount related to a rotational motion in the yaw direction of thevehicle, and the restriction object amount includes at least one of alatest value of a state amount related to a lateral translational motionof the actual vehicle or the vehicle on the vehicle model or a valueobtained by filtering the state amount or a future predicted value ofthe state amount, and a latest value of a state amount related to arotational motion in the yaw direction of the actual vehicle or thevehicle on the vehicle model or a value obtained by filtering the stateamount or a future predicted value of the state amount.
 8. The vehiclecontrol device according to claim 5, wherein the first state amountincludes a state amount related to a rotational motion in the yawdirection of the vehicle, and the restriction object amount includes atleast one of a latest value of a state amount related to a lateraltranslational motion of the actual vehicle or the vehicle on the vehiclemodel or a value obtained by filtering the state amount or a futurepredicted value of the state amount, and a latest value of a stateamount related to a rotational motion in the yaw direction of the actualvehicle or the vehicle on the vehicle model or a value obtained byfiltering the state amount or a future predicted value of the stateamount.
 9. The vehicle control device according to claim 6, wherein therestriction object amount includes a latest value of a yaw rate of theactual vehicle or the vehicle on the vehicle model or a value obtainedby filtering the yaw rate or a future predicted value of the yaw rate,and the permissible range for the yaw rate is a permissible range set onthe basis of at least an actual traveling velocity such that thepermissible range narrows as the actual traveling velocity, which is avalue of a traveling velocity of the actual vehicle, increases.
 10. Thevehicle control device according to claim 7, wherein the restrictionobject amount includes a latest value of a yaw rate of the actualvehicle or the vehicle on the vehicle model or a value obtained byfiltering the yaw rate or a future predicted value of the yaw rate, andthe permissible range for the yaw rate is a permissible range set on thebasis of at least an actual traveling velocity such that the permissiblerange narrows as the actual traveling velocity, which is a value of atraveling velocity of the actual vehicle, increases.
 11. The vehiclecontrol device according to claim 8, wherein the restriction objectamount includes a latest value of a yaw rate of the actual vehicle orthe vehicle on the vehicle model or a value obtained by filtering theyaw rate or a future predicted value of the yaw rate, and thepermissible range for the yaw rate is a permissible range set on thebasis of at least an actual traveling velocity such that the permissiblerange narrows as the actual traveling velocity, which is a value of atraveling velocity of the actual vehicle, increases.
 12. The vehiclecontrol device according to claim 6, wherein the restriction objectamount includes a latest value of a state amount related to a lateraltranslational motion of the actual vehicle or the vehicle on the vehiclemodel or a value obtained by filtering the state amount or a futurepredicted value of the state amount, and the vehicle model operationcontrol input includes at least a control input component whichgenerates a moment in the yaw direction about the center-of-gravitypoint of the vehicle on the vehicle model.